The price of the Radeon HD 4850 was cut, and can be found for as low as $120 after mail-in rebates, but the Radeon HD 4870 didn't go down because ATI's partners feel the card is too good:
The story with the 4870 is something else entirely. The Radeon HD 4870 512MB was supposed to drop to $149 with a mail-in rebate, but ATI's graphics card partners are resisting this as they feel that since the card outperforms the GTX 260, it should compete against that card. They instead are positioning the 1GB version of the 4850 against the 1GB version of the GTS 250 at the $149 price point.
One of our sources in Taiwan told us: "The ATI lineup is very strong, and we feel the 4850 should go against the GTS 250 and the 4870 against the GTX 260".