Yes but how much is the subsidy and how much goes towards expenses the hospital only has due to the resident? For example the subsidy also covers the resident's

Yes but how much is the subsidy and how much goes towards expenses the hospital only has due to the resident? For example the subsidy also covers the resident's malpractice insurance but the hospital isn't profiting from that. It also looks like there is the IME, a system where all Medicare payments are increased proportional to the number of residents intended to cover the extra work and expenses of training residents. So it's a rather thorny question and probably depends on the hospital (how many Medicare patients they have, etc). I imagine it's like NIH grants where the overhead is like 40% - substantial but I think the work done by the residents is likely to be a significant fraction of the value.