I've heard "different pots of money." So, money to a locums agency comes out of X budget or is reported as an expense one way, but pay to employees (even 1099 independent contractors) comes out of a different pool, and is reported differently. I am sure it likely has some tax implications, as well. Otherwise, I would think that the top suits would actually care that they are spending tens of thousands more than they need to by only going with big agencies, rather than having a few individual contractors.