$35 is about the going rate anywhere you go. How cheap did you think they were going to be?
If the mechanism is intact and it just needs the vent lid, those usually run about half that.
Don't forget the butyl tape and stainless screws.
It's probably best to go through FWC for the tank. Some FWC tanks fit like a glove with no room for error. There are TONS of different sizes and configurations out there, in my opinion taking some measurements and just calling the shop direct will save you a lot of time and frustration. They probably already have the one you need on hand anyways.
Wasn't sure found them on ebay for 20 plus 10 shipping but 5-7 day wait , prolly go down to camping world in the morning but never know if you dont ask ,D