It's a requirement by the FAA, too, to have a sign off for a test - ANY test - what I'm trying to get at is that it's the greed of the individual school that screws you with a charge, higher than normal dual rate, for taking a 170A flight test for the instrument rating - and it's the downright evil charging policies of a school that rips you off for a 170A for a CPL flight test.
This one is not the Authorities fault - though the charges that they do make for legitimate services are a disgrace (especially when you know where some of the money goes).