He's probably getting a little anxious and needlessly increasing his max bid (which could be $500 for all we know) to avoid a snipe bid defeating him at the end. There's a weird psychology surrounding eBay and auctions, people tend to spend more than they would usually be willing to spend.
I've seen many a time where two identical items have been listed on eBay, one at a BIN of $100 for example and the other as a .99 cent auction. You'd think that people would be inclined to go for the auction to have a shot at landing the item for less than the $100 BIN item, yet by the time the auction ends 2 idiots have pushed the price up to $160. Go figure.