a lot of what you are paying for is the high quality and guaranteed network connection that is not dependent upon a public internet provider. The contractual obligation cuts both ways, because they WILL fix it if goes down. Really , it is the difference between having a DSL connection and your own T-1 line. Sure the DSL is good, but it isn't guaranteed, and it is therefore much cheaper.
Now if a prop firm offerred bloomberg, THAT would justify the desk fees.
A related matter is that I wouldn't want to be in a trading room that didn't have a guaranteed land line connection like a T-1 line.