You can transfer it in your vault now, cool. I remember there was initially an issue with doing that. I have not seen a DC being auctioned as of yet but I would guess in excess of 200K.
Yup. Even 1 item inside and it won't allow it. But yes any empty box can be vaulted and used on any smp. As for the price, I think 1.5-3k is the general price. So for a DC approx. 81-162k. I'd have to check my logs but I think I sold my last DC of 2k per.
The last auction was at 195k that I say, so those were roughly 3.5k per... If it ends there, didn't check date/time.
I can confirm, The auction went for 192k, averaging about 3.5, though if you are selling directly to a player, they go more around 2k a box, even if it is a dc, just depends on your method of selling