From what I've read, if both players are an equal amount off, then they both win their respective showcases. If they both are under $250 and are both equal, then they both win two showcases, and as Bob has joked, the show will go bankrupt.
The closest it's been was one instance where someone was off by $30, and the opponent was off by $29. I think the clip is on Tony Harrison's site, tpir.tv