More time posting than coding
Whilst I generally agree that if you accept a rate you're happy with, the rate charged to the client by the agency shouldn't be your concern, there is one specific scenario where knowing this rate can be important:
Originally Posted by stek
Client --£600--> Agent --£500--> You
Client --£550--> Agent --£500--> Other Contractor
Agent has 2 contractors (who are for all intents and purposes equal in skill & experience) in the same client co, with the client co paying slightly more for you than the other contractor, despite you both getting the same rate from the agency.
Client has to cut budget and decides to reduce contractor head count. Who will the client choose?