That is because it is largely a work of fiction. The vast majority of a hospital's costs are fixed, not variable, so when they have to divide it up into individual "items", the amounts allocated are to each "item" or "service" are fairly creatively arranged.

Think about it - most of the stuff has to be there "in reserve" so to speak, with a fair amount of surplus to cater for surges of different kinds of sickness, so there is very little ability to match demand and supply. The actually variable stuff (e.g. drugs, saline, other consumables) is a fairly small part of the overall operating cost.