I do mine myself... I think I spent about $15 on a dedicated skull boiling pot, another $20 on some beauticians Hydrogen Peroxide cream for whitening, plus whatever propane I burn while boiling... actual boiling takes a few hours, depending on how much effort you put into fleshing out the skull first. If you've got the time, space, and desire, It's pretty cheap to get it done on your own.
"When a hunter is in a tree stand with high moral values and with the proper hunting ethics and richer for the experience, that hunter is 20 feet closer to God." ~Fred Bear