Sooner or later every founder opens a spreadsheet with two numbers in it: a senior engineer's salary on one side and a studio retainer on the other. Most versions of the in-house developers vs agency cost comparison end right there, and they end wrong, because neither number is the real cost of anything.
This article runs the honest math. Fully loaded salary, hiring time, management overhead, bus factor, and the value of being able to ramp down. It also names the situations where hiring in-house clearly wins, because pretending it never does would be selling, not analysis.
The fully loaded cost of one senior engineer
Start with base salary and treat everything below as illustrative arithmetic you should redo with your own market data. Suppose a senior engineer in a US metro costs $150,000 in base pay.
Base pay is the floor, not the bill. A widely used rule of thumb puts fully loaded cost at roughly 1.25 to 1.4 times base once payroll taxes, health insurance, retirement matching, and paid time off are added. Take the middle of that range and $150,000 becomes about $195,000 a year, or more than $16,000 a month, before the person writes a line of code.
Then come the costs that arrive on other invoices:
- Recruiting. External recruiters charge fees pegged to first-year salary, so a senior hire is a five-figure event before day one. Running the search yourself is cheaper in cash and expensive in founder hours.
- Equipment and tooling. Laptop, software licenses, cloud sandboxes, CI seats. Small individually, persistent forever.
- Ramp time. Even excellent engineers need months to become productive in an unfamiliar codebase and domain. You pay the full loaded rate during the ramp.
None of this is an argument against hiring. It is an argument against comparing a salary to a retainer as if they were the same kind of number.
What a retainer actually buys
A retainer is not a discounted full-time engineer, and any comparison that treats it that way flatters the agency side. ETREXIO's retainers start at $5,000 per month, and what that buys is not a block of typing hours. It buys a system that is designed, built, shipped, and then operated: monitoring, fixes, iteration, and the accumulated context of the people who built it.
Two things separate modern studio math from the agency math of a decade ago. First, AI now carries a growing share of the routine work. At ETREXIO the team is two senior builders plus an AI workforce, always human-in-the-loop: AI drafts, humans review and decide. Second, a retainer prices an outcome, so the incentive is to solve the problem with less effort, not to bill more of it. Our average client relationship runs around five years, which is worth noting only because it shows a retainer is not inherently a stopgap between hires.
The honest tradeoff: you get a slice of a senior team rather than a person who is exclusively yours. If your roadmap genuinely needs forty focused hours a week from one dedicated mind embedded in your standups, a retainer is the wrong instrument, and a good studio will say so.
The costs that never make the spreadsheet
Three factors move the outcome more than salary does, and none of them appear as a line item.
Hiring time
A senior search commonly takes months from posting to start date. Every one of those months is a month of features not shipped, plus the founder attention spent on sourcing, interviews, and negotiation. A retainer engagement typically starts producing within weeks, because the team and the working system already exist.
Management overhead
An engineer needs a manager. Someone must set priorities, review work, run one-on-ones, and handle growth conversations. In a small company that someone is usually a founder, and the hours come out of sales or product. A studio brings its own management, which is part of what the retainer actually pays for.
Bus factor
One engineer is a bus factor of one. If they leave, the knowledge leaves with them and the hiring clock restarts from zero. Maintaining more than 50 products has taught us that the costly part of software is rarely the first build. It is year three of ownership, when the original context lives in one person's head. That risk exists in both models; the difference is who is contractually obliged to manage it. Ask any studio, ours included, how knowledge is documented and what happens if a key person is unavailable.
Flexibility is worth real money
Employment is a commitment. A retainer is an option, and options have value that never shows up in a naive cost comparison.
If revenue dips, winding down a retainer usually means a notice period measured in weeks. Winding down an employee means severance, morale damage across the remaining team, possible legal exposure, and the near certainty that you cannot rehire the same person when budget returns. The reverse is also true: scaling a retainer up for a launch quarter is a conversation, while scaling headcount up is another multi-month search.
For a company with lumpy or uncertain revenue, this flexibility alone can justify a price premium. For a company with stable, growing engineering demand, it matters far less, which leads to the cases where hiring wins outright.
When in-house wins
Sometimes the spreadsheet should lose. Hiring in-house developers is clearly the right call when:
- The software is the moat. If your core algorithm, data model, or domain logic is the reason the company exists, that knowledge belongs on your payroll, compounding inside your walls.
- The roadmap needs ten or more people. Past a certain scale, coordinating full-time staff inside one company is cheaper and faster than coordinating across a vendor boundary.
- Regulation or security demands it. Some environments require embedded, badged, background-checked staff, and no external model fits.
- Engineering culture is part of the product. Companies selling developer tools or infrastructure often need their builders and their users to be the same kind of person.
Plenty of companies land on a hybrid: a small in-house core owning the moat, with a studio handling adjacent systems, internal tools, and overflow. The models are not enemies. They are instruments for different jobs.
Run the comparison for your own company
One evening, five steps:
- Compute the fully loaded monthly cost of the role: base times a 1.25 to 1.4 multiplier, divided by twelve, plus tooling.
- Add an honest allowance for the management hours the role will consume, priced at the manager's value, not zero.
- Estimate months from starting the search to full productivity, and put a cost on the features that wait.
- Price the bus factor: what would it cost to reconstruct this person's knowledge if they left in eighteen months?
- Compare that total against a retainer scoped to the same outcomes, not the same hours, and check which one you can exit gracefully.
If the retainer side of that math looks interesting, talk to us and we will walk through the numbers against your actual roadmap, including the scenarios where we would tell you to hire instead.
Frequently asked questions
Is it cheaper to hire in-house developers or use an agency?
For a single senior role, an agency retainer is usually cheaper once you count payroll taxes, benefits, recruiting, tooling, and management time, which push a $150,000 salary well past its sticker price. In-house becomes more economical when you need multiple dedicated engineers working full time on one product.
What is the fully loaded cost of a software developer?
Fully loaded cost is base salary plus payroll taxes, benefits, insurance, equipment, tooling, recruiting fees, and the management time the role consumes. A common rule of thumb multiplies base pay by 1.25 to 1.4, so a $150,000 engineer typically costs the business closer to $190,000 or more per year.
When should a startup hire in-house instead of using an agency?
Hire in-house when the software itself is your competitive moat, when the roadmap needs ten or more people working full time, or when regulation requires embedded staff. At that scale, coordination inside one company becomes cheaper than coordination across a vendor boundary, and the domain knowledge belongs on your payroll.
Can you combine in-house developers with an agency?
Yes, and many companies do. A common split keeps core product and domain logic in-house while a studio owns adjacent systems, internal tools, monitoring, or overflow work. The arrangement works when ownership boundaries are explicit, so both sides know who is accountable for each system and its uptime.
