I got the batteries for $12 each, and the Integrated Circuits were like a couple dollars for 10 of 'em.. I wouldn't charge anything, myself. No real need to change the capacitors unless they are damaged. In some cases the board can be saved if it isn't too bad. I have seen everything from completely useless to almost pristine save for a bad battery. Got a pile of 'em here. One or two are savable with some work.
I also remove the ICs and replace them with a socket. Then plug new ICs into the socket.
Conformal coating is merely clear Krylon.
Anyway those guys are running a business. I can see charging what people will pay but honestly it's maybe a half hour's work to refurbish one, and the parts are peanuts.
1966 109 5 door wagon 300Tdi "spermaceti fueled"
1994 RRC LeWiB "ruining the air behind me"
All my troubles are Rover