I came with that last night in our 10-man hard mode ToC. For that, you need at least 50 emblems of triumph.
That way, before the raid, if your rings or trinkets aren't good, you can go ahead, buy the emblem trinket/ring, equip it for the raid, and considering how the raid is short and the vendor is right outside the entrance, you can keep refreshing the 2 hours timer on refund, and at the end you can just give it back and save your emblems for Tier 9/9.5.
This is not very valid for other pieces of gear, that don't work very well without enchant/gems, which makes the item bound to you and impossible to refund. Except if it's a bigger upgrade even without enchants/gems.