Frequently Asked Questions:
A: 240 times a day it has a chance of creating items; the more battles that were fought during the previous day, the more likely items are to be created. There is no "refreshing" per se anymore.
A: That's because rare items spawn directly into auctions.
(At very low levels, buying the best you can find in the store is fine; a little later, you may be better off renting.)
A: The store will give you 80% of what it would sell the item for. If you've been upgrading at the blacksmith, this will be far less than you've paid for it; the blacksmith charges a hefty premium. Except for very low-level items, you'll probably get more of your money back by selling through Auctions.
A: Since CB is a free-market economy, the answer is, "whatever someone is willing to pay for it." To get an idea, search expired auctions (with bids, of course). This will show you items from the past 6 months. Another clue is the "Average price - NW" (average price an item auctioned for over its NW) column in the Stats -> Items -> Overview page.
A: Yes, but if you spend your BA fighting instead, you will almost always do better financially. Especially when you count the XP you are earning as well.