I've sold 3 images outright (or 2 definite, one I'm currently negotiating)
Prices were $400 (this was a stock image with few sales) $1500, (a more popular image but with under 100 sales) and I'm currently in negotiation with a major beauty company for another for $3500. This is a simple image but with sales in the many hundreds. In the first 2 examples the companies involved drew up contracts acknowledging the rights of previous buyers but which granted ownership to the buyer, the last one is a bit tricky as the companies legal dept. are balking at the fact that so many have already bought it and I may have to re-draw the image ( for which they are offering extra money for a custom artwork)