Actually it should take it off the current price, even if discounted. Otherwise people would pay more than using the Online TurboTax site. It's always provided additional discount when I've tested it. If it's $5.00 off for Deluxe, user should be charged $34.99. At least that's the way it has worked for other sites I've tested such as USAA or PenFed. Deluxe through USAA is $10 off, so users there have been paying $29.99, and that is what is displayed there on the product page when going through the steps at their special promo link.
I'll see if I can trace that ebates route some more.
