It depends the field. Some companies in some locations will charge north of $250 an hour for some profiles, and more for an end to end product custom software. We shipped custom ML platforms for large organizations as part of our activities. The applications allowed their marketing and sales department to train models or load models on their data according to their workflow. Custom made. Some solutions allowed them to send personalized offers to millions of subscribers.

For some clients, on call 24/7. Going to the client. Meeting their people. Handling regulatory paperwork for some projects in regulated fields. Even taking care of importing the hardware for them. Interfacing with their data people and learning their third party vendor's billing systems.

As with everything, it depends on the domain, the service, the support, and generally speaking what they're going to do for you, and which part or parts they're tackling.

Repeat business is common as when these organizations like the outcome, they want more. So that's my two cents from the vendor perspective.