If you are familiar with the 8 series, the GTX 275 (single card) is about as powerful as 3 8800GTX ACS3 cards in tri-sli.
The expensive GTX 295 co-op is like 2 GTX 285's. So as masterjaw said you did hear wrong. These are much more powerful cards but I would wait about another month and see if ATI releases their new direct x 11 cards and create a price war giving you a better deal...