There are quite a few watermelons, but I feel the Original is the only one that's deserving of its price. A distant second would be the Red. The Original is one of the few LPS out there are actually looks just as good in person as it does in photos. Also, it's combination of color, texture, and pattern really set it apart from the others.
If you can trace the lineage of yours back to Ron's, I wouldn't expect a frag of it would go for any less than $150, unless it was a friendly hook up or trade.
I don't even care for LPS, but this was one of two that I just had to have.