On my realm, primor saronite sells for over 2k on ally side. As i am horde i can buy them for 1200-1400, depending on the day. (they are listed on AH from 1500-2k though, so i buy them through trade or in exchange for cheap raw epic gems). Even with the loss of getting my money back to horde, that is a nice few 100s k without much effort. However i buy mostly mats on ally side and trade those back to horde, to avoid the 15%