Yeah but it's often not real billing. It's just to put a price on it so internal departments don't waste a ton of company resources because it's 'free'.

I work for a very large enterprise also and we've been instructed to stop internal billing for everyhing less than 10k, and everything above 100k must be compensated in other ways, like shifting of responsibilities or personnel between teams. This was done because various departmental interests were basically trying to 'make money' at the expense of other internal departments and creating a complex mesh of internal contracts that was only wasting a huge amount of overhead :)

The problem with this thing is that it can become a goal of its own and some departments think they are making a ton of money even though they're only shifting internal funds and causing huge expenses in finance.