If you choose to "buy" one from another player, basically you give them the item on the market that you want heirloomed plus a ridiculous amount of cash, and they heirloom the item for you and give it back. They used to cost 400K 200k per point, but are now 700K minimum due to the inflation of less people willing to sell their heirloom points plus sellers knowing that the new items are making buyers desperate.
Fixed: Do not underestimate cRPG inflation