1. Mandatory Food (or other daily maintenance costs)
Ah, food - the great money sink. While it might be somewhat challenging at lower level when money is scarce, it's merely an annoyance at higher levels. And it grows to be a big annoyance over time. Let's just assume that —- like having to excrete wastes as well —- eating is just something that happens "behind the scenes," okay? Unless it's something special - like having a feast with the king or eating an enchanted apple - I don't want to worry about it. I don't want to pay a tax on staying alive.
I shouldn't have to say this, but I will anyway - non-mandatory food (where, for example, an apple gives you a slight health boost) is fine.
Exceptions: If it's a "survival fantasy" kind of game - like Ultima Underworld or Arx Fatalis, where food is not something taken for granted by anyone - then the above doesn't apply. I actually enjoy the verisimilitude. It's no longer an annoyance, but a key part of the narrative. (Hah! I caught a fish!)
Strangely, the cost of staying at an inn (which is functionally equivalent) usually doesn't bug me - especially if there is a "free" alternative somewhere in the game that I can return to if I'm feeling particularly skinflint-y.