The number 5 in 5800 must denote the Geforce version, even though we now talk about a numberless FX instead of a GeForce 5.
These names have not been confirmed by Nvidia at this time. The company says it will disclose the numeric part of the name with the first card announcements that we expect in January.
As for the pricing, we have some clues for you. Nvidia mentioned in one presentation that the card will be in the high-end price range, mentioning the Geforce 2 Ultra and we all know how expensive that was.
The Geforce FX 5800 Ultra will be for rich gamers who do not need to worry about money, since we expect they'll have to fork out around $499 (US) to own one.
The normal version - called Geforce FX 5800 - should cost $399 just as much as the TI 4600 cost when it was introduced.
Source : TheInquirer