I renewed my CASA few months ago and was under $200 including CASA rubber stamp charge.
Right now in New Zealand there is no CAA rubber stamping charge.
You go to your DME or AMA and complete your medical, if you go to a DME they send your details to an AMA who then assess the data and issues the medical providing everything is in order, or if you go to an AMA everything is completed on the spot without any input from CAA. CAA are just notified of the medical completion/result. Just the way it should be, CAA approve these guys to issue the medicals there's no need for any CAA input.
So far as rubber stamping by CAA/CASA goes this is ridiculous, a parallel would be CAA/CASA approving every single flight for all pilots.
I don't see any need for CAA to be putting their hand out for more money.