Sadly this is how hospital stays are conventionally billed. The cost of being admitted covers only the bed and routine nursing, literally everything else is billed separately. As unfair as it is, the best patients can do is vehemently question the necessity of any interaction with a physician, or else get billed for it. And good luck with that if your case is complicated and you're getting referrals to a wide range of specialists.

And honestly, when you're admitted to the hospital unexpectedly, you're probably not in the frame of mind to be questioning everyone who comes by. I know when I was in for a few days, I only recognized the name of one of the hospitalist doctors that later billed me. And the bills can come months later!