Yes, this is a sucker bet, especially with a 10 showing. This is equivalent to taking insurance. The casinos here always offer "even money" in this situation and both dealer and other players will treat you like a fool if you decline it. However the expected value of a blackjack when the dealer has an ace showing is 1.04 units, better than the 1.00 units you’ll get by taking the even money. So unless you’re a card counter and know the remaining deck to be 10-rich then always decline even money. I’m glad my basic strategy helped you win.