So yes, Frostmourne is a sweet sword, and yeah these real-life replicas are great (like a couple of thousand dollars great). But $20,000? That's how much the winning bidder put up in the Weaponmasters auction to get a limited edition low number sword, a gaggle of extra goodies, and of course the real reason someone would spend five figures on a collectible: membership in the Arthas' Army of Disciples club. That's a lot of cash.
Blizzplanet has a list of all the bidders (for public humiliation purposes?) -- the "winner's" (if you can call someone out $20k a winner) name was Xeophonix, apparently from Italy. Only the first two bidders went all out -- there's one more $20k bid, and then it drops to $12k, $5k, and then on down from there to the much more reasonable bids around $500. But grats to Xeophonix -- hope the $20,000 sword is worth it. And watch your back -- we don't know exactly how you kill a Lich King, but if Weaponmasters didn't quite get Arthas' sword away from him for good, you might have an angry Menethil/Ner'zhul showing up at your door.
[Via MMO Champion]