Important note: the prices are not different. Just that more 5-star hotels are shown in the search results to Mac users. If they were charging more for the same hotel, it would be evil not brilliant. :)
We tried both adjusting individual prices for Mac users (and didn't see any statistical difference from the price sensitivity for non-mac users, same as we didn't see statistically significant differences between older and newer Windows version users), and skewing the search result price range for Mac users compared to non-Mac users (and we certainly saw statistically significant improvements there in terms of average dollars per room-night). In the long run though, although we proved to ourselves it worked, the Mac userbase back then was so small that the overall bottom line effect wasn't big enough compared to the engineering and marketing effort to keep it working - I think it all vanished in the big 2004 rewrite of the site's back end.