No plaque price explained for a "hobbyist".
For a properly cleaned skull that has been adequately degreased you should expect to pay $100+ at a minimum.
It's taken me a while to fine tune my process using beetles or maceration, then degreasing in a high enough temperature to not deteriorate the bone and to pull out as much grease as possible within a reasonable amount of time. 99% degreasing would take a month or more at a fine tuned temp and constant fluid changes. I shoot for 1-2 week degrease and this produces, IMO, an above adequate skull.
A quick boil, power wash with a overnight whitener produces a sub par skull which most are pleased with. This is actually the process I use on out of state hunts. I can easily tell the difference between these skulls and others I've done after 6-12 months of hanging on the wall. I also wouldn't charge as much for this process either. It takes less time, produces less quality and less overhead.
Ignore the people that say you charge too much. Let them open up a skull cleaning side hustle to under cut you and dee how long they stay open. With that said, southern taxidermy is cut throat. Produce a quality product, charge enough to be worth it and go about your day.
If making money is priority #1 then move West and charge $300 for a cleaned skull.