A 1972 Les Paul Custom with completely original parts, no repairs and in great condition could possibly sell for 4000-5000, maybe more, depending on the market at the time. But, since most instruments of this age have some playing wear and repairs made (and or needed), you might only get a couple thousand for it. You'd get more money selling to a private party instead of a dealer, but that can be more of a hassle and riskier. Pictures could help narrow down the price. Steve