It depends...
1) If you're desperate to get a pack right after release date, resellers will make you pay.
2) If people buy but don't resell and there's not too many in circulation, supply < demand
People won't let them go for anywhere near <500 that's a given. This is the most hyped up pack of the entire series. And when you do buy a packfor +500, you'd either keep or wear them and that's one pack less in circulation.
Resellers are cashing in people this X'mas off this pack. Before release, pre-order sites are already charging a fortune. After release, resellers aregonna charge a fortune. It's hit or miss, release day for retail, otherwise you won't see that price again. Ever !
$310 for this pack is super rare, the window for it is small (only 12/20). If resellers paid $310 for it, they'll look to double. They'll set BUY ITNOW prices high, and when people do buy they know that the demand stands at their price point and it'll never go down. They're anticipating that thisis probably the last chance to get XI and XII before Jordan floods the market with fusions.
$450 - 600 and it can go up. See DMP's