The data. This is the main one. If you work with clinical records, a law firm's internal documentation, HR files or anything you cannot justify sending to a third party, self-hosting removes the problem at the root instead of managing it with a contract.
The cost. With an API you pay per use, so your product's success inflates your bill. With your own infrastructure the cost is fixed: past a certain volume, each new user is practically free.
The control. Nobody deprecates your model, changes its behaviour overnight, raises the price or rate-limits you at the worst possible moment. The version you validated is still there tomorrow.
The clinical platform I co-founded and operate runs on an open model self-hosted on our own GPU. It is not a proof of concept: healthcare professionals use it and clinical data never leaves controlled infrastructure.
It depends on the model and concurrent usage, not on your company's size. For an internal assistant with a quantised mid-size model, a single professional GPU of 24 to 48 GB usually serves dozens of concurrent users. Sizing comes from measuring your case, not from a table on the internet.
Above a certain volume yes, because cost stops growing with usage. Below it, the API wins. We calculate the break-even with your numbers before you buy anything, and sometimes the conclusion is that it isn't worth it.
Yes. A rented GPU at a European provider gives you the same data isolation with no upfront investment, and it's the sensible way to start. If volume grows, then you consider buying.
Delivered documented and monitored for your team to run. If you prefer me to run it, a monthly arrangement covers updates and incident response.
It removes the third-party transfer, usually the hardest part to justify, but it is not an automatic stamp. Legal basis, access control, minimisation, retention and log hygiene still apply. It does simplify the analysis a lot.
Tell me what you want to solve and with what information. I'll tell you whether self-hosting pays off for you, what it would take and what it really costs.