There is an alternative to buying "used". About 3 times a year, the BMG Music record club (NOT to be confused with Columbia) holds really excellent sales . . . the last time (early December) I bought 22 discs for $149 ($6.77 a disk, including shipping).
Their only fault is that it take quite awhile for BMG to get the very latest music from some labels. (Once you get over the initial membership requirements of buying "one at full price" to get the 12 free, there are no more "automatic shipments".)