When businesses are comparing developers for ExpressionEngine work, the hourly rate is usually the first number that gets attention. A generalist agency billing at a lower rate looks attractive on paper. But the total cost of working with someone who does not specialise in ExpressionEngine is almost always higher than the headline rate suggests.
Time spent learning the platform
ExpressionEngine has its own conventions, its own template language, its own addon ecosystem, and its own upgrade path. A generalist developer working on an ExpressionEngine site for the first time will spend time learning these things. That time is billed to you. A specialist who has worked on ExpressionEngine sites for years already knows the platform, which means the same task takes less time and the result is less likely to require revisiting.
Diagnosing problems correctly the first time
When something goes wrong on an ExpressionEngine site, a developer who knows the platform can usually identify the cause quickly. A generalist will often start from first principles, working through possibilities that a specialist would have ruled out immediately. Diagnostic time on an hourly rate adds up quickly, and an incorrect diagnosis followed by an incorrect fix adds up even faster.
Avoiding the mistakes that specialists do not make
Experienced ExpressionEngine developers have encountered the same categories of problems repeatedly. They know which addons cause conflicts, which upgrade paths require care, and which template structures create performance problems. That accumulated knowledge means they do not make the mistakes that come from unfamiliarity. Those mistakes, when a generalist makes them, are billed to you as time to fix them.
The retainer relationship
A specialist who understands your ExpressionEngine site well can provide genuine ongoing support efficiently. A generalist providing monthly support on a platform they know less well is less able to spot problems proactively, slower to diagnose them when they occur, and less equipped to advise on when and how to extend the site. The retainer cost may appear similar but the value delivered is significantly different.
The long view
The question is not what a specialist costs per hour. The question is what a given piece of work costs in total, what the risk of that work going wrong costs, and what the accumulated effect of informed decisions versus uninformed ones costs over several years of maintaining a business-critical website. On that basis, a specialist is almost always the more economical choice.