For an app spending between €10k and €300k a month on acquisition, the choice between an in-house UA team and a mobile growth agency comes down to three things: what it costs fully loaded, how fast you can change direction, and how much control you keep over data and creative. Below is how the two compare in practice, and the hybrid most scale-ups land on.
Cost
A credible in-house growth function in Paris, Madrid or a US hub is a UA manager, a creative producer, part of a data analyst and part of a CRM manager. Fully loaded that is €180k to €300k a year in Europe and materially more in the US, before tools (MMP, creative testing, ASO suite, CRM) which add €30k to €80k. That team is efficient at scale, but at €30k a month of media it costs more than the media.
An agency retainer for the same scope typically runs 10 to 20% of media spend with a floor, and includes the tools, the creative testing cadence and the senior time you would otherwise hire for. The break-even is usually around €80k to €120k of monthly spend: below that the agency is cheaper, above it in-house starts to win on cost alone.
Speed
In-house teams are faster on product-side changes: a paywall test, an onboarding tweak, a new event to track. Agencies are faster on channel-side changes: a new platform, a creative format that started working for other apps last week, a SKAN or consent update that would take an in-house team a quarter to learn. A team that runs 20 apps has already seen your problem on another account.
Control
This is where most founders hesitate, and rightly. Three things should never leave the company whatever model you pick: ad accounts and MMP in your name, first-party data in your warehouse, and creative source files. Any agency that wants to run campaigns from its own accounts is building leverage, not results. Ask before signing, and read our 12 questions for a UA agency.
Where each model fails
In-house fails when one person carries UA, creative and reporting alone: the account runs on autopilot, tests stop, and nobody audits the traffic. We have seen 80% fake installs go unnoticed for months on accounts with a full-time manager.
Agencies fail when they are paid on spend and measured on CPI. Both incentives push toward volume. Fix it contractually: pay on a scope, measure on payback and cohort ROAS, and require a monthly incrementality check on every network source.
The hybrid most scale-ups use
One in-house growth lead who owns the number, the roadmap and the relationship with product, plus an agency that runs channels, creative production, ASO and the data layer. The lead spends their time on the decisions only an insider can make; the agency brings the benchmarks, the tooling and the hands. At Scalebay this is the model behind most of our case studies, and it is the one we recommend from roughly €20k a month until the app is big enough to hire a full team.
Not sure which side of the line you are on? Send us your current spend and team and we will tell you honestly, including when the answer is to hire.
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