Project fees and retainers solve different problems for an AI agency. Here's how I decide which one fits a given client, and why I stopped defaulting to one over the other.
For the first year of Allwebzone, I only sold fixed-scope projects. Build the agent, deliver it, invoice, move to the next client. It felt clean. It also meant I was constantly restarting the sales process, and every project ended with the client’s system frozen in whatever state it was in on delivery day, slowly drifting out of date as their business changed around it.
Retainers solved that problem. They also created a new one: clients who wanted retainer-level access without retainer-level scope, expecting unlimited requests for a flat monthly fee. Neither model is universally right. The mistake is picking one and applying it to every client regardless of fit.
A fixed-scope project works when the deliverable has a clear finish line. Build an onboarding automation, ship it, done. The client knows exactly what they are paying for and exactly when it ends. I still default to project pricing for anything with a defined build phase, because ambiguity about scope is where agency relationships go wrong, and a project fee forces that ambiguity to get resolved before work starts.
The limitation is obvious once you see it: agent systems are not static. A workflow that fit a client’s business perfectly at delivery starts drifting the moment their business changes, and a one-time project has no mechanism for keeping pace with that.
The exact architecture, memory layers, and delegation patterns I use to run 50 agents across two businesses.
Get the AI Agent Blueprint →A retainer is not really about ongoing work. It is about ongoing attention. My retainer clients are not paying me to sit idle waiting for requests. They are paying for a system that gets monitored, adjusted, and improved as their business shifts, without them needing to re-engage a vendor relationship from scratch every time something needs to change.
This only works if the retainer has real boundaries. My retainers specify a defined number of monitoring hours, a response time commitment, and a clear escalation path for anything beyond the scope, priced separately. Without those boundaries, a retainer becomes an all-you-can-eat buffet that erodes margin every month it runs.
I ask one thing before quoting a new client: does this business change fast enough that the automation will need meaningful adjustment within six months?
A solo consultant automating a stable, well-defined onboarding flow probably does not. That is a project. A fast-growing agency whose client mix, tools, and processes shift constantly probably does. That is a retainer. Applying project pricing to the second case means constant scope negotiation for every small change. Applying retainer pricing to the first case means charging monthly for a system that mostly does not need touching.
Most of my current clients end up on a hybrid: a fixed project fee for the initial build, followed by a smaller monthly retainer for monitoring and incremental adjustments. The project fee covers the heavy lift. The retainer covers the reality that automated systems need occasional human attention to keep working as conditions change around them.
This structure also solves a sales problem. A large project fee up front is an easier commitment to get than an open-ended retainer from a new client who has never worked with you. Once the project delivers real value, the retainer conversation becomes much easier, because the client has already seen the outcome instead of being asked to trust one in advance.
I no longer offer unlimited-request retainers at a flat rate. Every retainer I write now has a defined scope of hours or request volume, with anything beyond that billed separately. The unlimited version sounds appealing to sell but is structurally impossible to price correctly, because usage always expands to whatever the client thinks they can ask for.
Pick the pricing model based on how fast the client’s business actually changes, not based on which one feels easier to explain on a sales call.
The newsletter covers pricing structures for AI service businesses with the actual numbers behind my project and retainer contracts.
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