Hm. Well, the price of the items notwithstanding, the PCs didn't make it through by being terribly tricky, or by using lots of their abilities. They made it through by being lucky and/or through a misreading of the rules.
Either way, I don't see as the PCs really had opportunity to learn from the encounter, so they probably shouldn't get a whole lot of XP for it. This is typical of surviving such a challenge. To quote the 3e DMG, pg 166:
"The XP chart doesn't support awards for encounters eight or more Challenge Ratings above the party's level. If the party is taking on challenges that far above their level, something strange is going on, and the DM needs to think carefully about the awards rather than just taking them off a table. See Assigning Ad Hoc XP Awards."
So, the correct answer is not Dimwhit's "Extend the table". Nor is it Magic Slim's "No XP". The DM needs to consider an Ad Hoc award.