I suspect people are more concerned about getting their money out at all, than just waiting a month. Why else would you pay a 20% premium?
If you were buying coins now, you wouldn't be wiring funds to Gox and paying a 20% premium. The only people who would pay that are those who (unfortunately) have fiat funds there waiting already.
Also, Gox would be for traders. Try trading on Stamp, it is hard. You could keep your coins on Stamp and trade with some on Gox as there is the action.
I trade regularly on Stamp, without any major issues. TBH, it tends to be a bit less erratic, IMO.
I take your point though that traders are looking at relative prices, rather than absolute prices. I'd still be a bit concerned about Gox's future, considering the way the market is pricing the risk already.