If you pay via snail-mail with check or money order your item won't appear till check clears. The seller determines the bid increment. Because you are both registered users this should not occur. But of course the world isn't perfect and folks can ignore email and telephone calls. If this doesn't work let us know and we will investigate and possibly ban them from the site.
Every reasonable precaution is taken but problems do occur.
Once again report them. List your experience in the 'Feedback' section. This will warn other users. You may also contact the next highest bidder by viewing the 'Bidding History' and offer the item to the next highest bidder. Go to 'Your Auctions' and click the number of bids to view the bidding history of a closed auction.