It might be wise to wait a week to determine prices after the set has been spoiled and more info is given on distribution quantity. Right now speculation and limited information on print quantity are making pre-orders absurdly expensive, but that could easily change in a week with new information.
Even at this moment though, $300 is beyond reasonable. $220ish maybe if this set is actually as good and as limited as speculators expect? But honestly at that price I would still only consider getting a box if I wanted to keep it sealed as a collector's item. Otherwise I would much rather just get a playset of thoughtseize for that price.
My vote would be for selling packs, 3 per person limit, first come first serve.