I think it's fine at the moment. If the buy prices are high, but the sell prices low (I doubt he's selling for even 200 gold) we won't have a problem. One thing I have noticed, though, is that many cards have sell prices very close to their buy prices (I think
Goblin Swarms was 27g to buy, 25 to sell at one point). This does concern me a fair bit, but I'm sure MarcinS has it all under control.
That said, I agree that another reset would be catastrophic. Now that tengwars and promos are so rare, I'd be even more gutted than last time if I lost mine.