It seems to be common practice now for folks selling no-name DVD blanks to market them as "YX-ZX", "Y" being the rated speed, "Z" being the maximum speed that can be achieved on some equipment, usually with hacked firmware.
I bought a lot of DVD-R 1X media that other folks successfully were burning at 2X, and I guess after reading all those posts, somebody figured that they ought to be able to cash in on that sort of trend.
I don't have a problem with this at all, it seems pretty clear to me that when a disc carries a double rating, the speed you will get is hardware dependent and may exceed the original engineering specs. Otherwise, what would you suppose is the difference between "4X" rated media and "2.4X-4X"?
Anyway, even the before rebate price is reasonable, with the rebate included, it is an absolute steal. If you're not happy, you could probably eBay them, less the discs you burned, and still do very well.
Just my 2¢.