Sapphire is obviously trying to sell all of her remaining HD 5830's and HD 5850's.
These are the outdated 40nm Cypress chips, but Sapphire really has a good strategy in getting rid of them:

- new cooling
- lower price

With lower price, we can understand that the HD 5830 will be sold for 95 euros and the HD 5850 for 110 euros. This means that the 5850 will be sitting between the HD 6790 and GeForce GTX 550 TI.
With the benchmarks showing that HD 5850 is obviously the faster one, this HD 5850 sure is the best price/performance.
The HD 5830 is equal to HD 6790 in performance, but with the lower price tag.

Put HD 5850's in Crossfire and you have a GeForce GTX 580 for half the price!

Source : http://www.kitguru.net/components/graphic-cards/zardon/sapphire-hd5830-hd5850-xtreme-edition-review-crossfirex/

Source : http://be.hardware.info/nieuws/22810/sapphire-lanceert-hd-58305850-xtreme