With patch 4.01 looming, I'd been agonizing over whether to purchase heirloom maces for my planned Enhancement Shaman alt. This class prefers slow swinging maces over the fast daggers I already own for other characters, but none of the other classes I plan to play would want to use them. On the other hand, the maces are costly at the Argent Tournament (overpriced compared to other heirlooms), and my current supply of emblems would not buy even one at the newly increased level 85 prices.
In the end, I decided to take the maces, and I also traded in all the emblems on my warrior for the heirloom staff to use on my second server.
In principle, both characters could or perhaps even should have used the emblems/justice points for actual gear for themselves instead. That said, the thing I realized as I pondered this question was that it's only virtual money. I got a good deal if I actually end up using the things, and, if I don't, my "losses" are digital points that I'm going to earn more of anyway. Sometimes, it's worth remembering that.