My vet charges $5 or $10 to clean sheaths (can't remember). I generally just clean them myself but I have one gelding that won't drop. I get his done when his teeth are done (she charges $25 for the teeth floating, $20 for the dope). I love my vet. Oh, and $50 for a farm call.
I've got 6 horses and to have all teeth floated and shots given (I buy the shots, she just gives them) I think it cost me $300 for all of them last time.