actually whats happening is common. what happens is that someone very early on bid quite high on an item that they really want to win. even if they bid 100 dollars on an item thats currently showing 20 dollar bid amount, the amount ebay will show is the amount of the next highest bid plus the "bid increment" usually a few dollars, thats set buy the seller. so even tho the listed current price is 20 dollars and you bid 40 dollars the new item price will rise to $40+bid increment or about $45. however since the earlier bid was $100, it will show that you were outbid by another bidder (since he bid 100, they system will automatically increase his bid to keep it the highest untill the amount exceeds his $100 bid) . this other bidder is now obligated to pay the $45 amount that you were willing to pay, even if he had bid $100.
if you bid again at 60 dollars, the other bidder will then have to pay $65 even if he had a $100 bid placed. you can keep bidding untill you either are no longer interested in paying that much, or you will reach a point where you outbid the other bidder. in this case that would have to be over $100. when you look at the bid list, it shows the outbid people, and the highest bidder, however his MAX bid remains a mystery untill someone else exceeds that amount, or the auction ends, and even then im not sure if you see his max bid, or only what he ended up paying, which may be much lower than his MAX bid, but higher than your MAX bid.
hope this helps, and if i missunderstand any of this i hope someone else steps up.