Learning how to price items

parts that are in demand are easy to sell for a fair price. parts not so much needed, are worth less. some people want every last $$ possible, other people have parts they really don't need. and price parts to help people out. some people are in the parts business, and know what is a fair price. other people are just out to screw whoever they can. clear as MUD!?? LOL
or take feebay prices and divide by 2, take cl prices and generally divide by 5.
and if a sensitive guy, price something ridiculously high and get laughed at. but not in print. no comments in the " for sale" sections!!!
sorry no way to help!