What's the point?
If you nibble it up to €15, you might be missing out on sniping it at half the value. Other bidders will just end up competing with you and artificially inflating the price.
If you're prepared to pay €40, you should just snipe at that value. You'll get an idea of the market value soon enough at the end of the auction If you're only prepared to pay €10 and it goes for €15, then that's life, someone else wanted it more than you.
putrid