Here's the stock exchange: the median prices paid historically (and typically matching VG+ 'very good plus' condition) can be seen @ Discogs and retrieved from my collection by price filtering (in the query front-end). Be aware that minimum prices often had been paid due to bad record conditions (< = VG 'very good') and maximum prices for top conditions (>= NM 'near mint'). The gap between VG+ and NM may be 50-100%. The market for the future @ Discogs, i.e., the asking prices may vary, e.g., if the record is rare and in demand. You should also check how many people 'have' and 'want' a particular record (-> query: want-have-ratio) to make your buying decision. Statistics of my collection show that most records cost <10€, and on the other side of the spectrum, find quite a few worth > 100€. (My highlights include Prince: Black album (original 1987 issue), 319 promo single, undertaker promo CD, and Madonna: Erotica (original UK picture disc), among others. But: many cheap records are damn good-consider that!