If you'd be attached to your heirloom why would you put it on the market in the first place? I've had the same problem, I just wanted to trade heirlooms, but how can I take a 200k offer when I have to buy 400k for the new one. So, I've sold it for 400k, bought what I wanted for 400k, no problem at all for me. Sure, it are kind of unrealistic prices but since the values of gold and heirlooms are extremely subjective, you have to go with the majority. Still, people will find the balance sooner or later, simply by virtue of not getting their trades.