Doesn't mean he's marketing it like that, he just put two letters together. The "XP" in Windows XP stands for eXPerience, so saying that a site with XP in the name is trademarked is like saying that 8GC would be trademarked because GC stands for Gamecube. Shouldn't be any trademark issues. I'd guess low to mid $xxx
something generic like xp has very light trademark rules. He can sell this without worrying about the trademark.