There actually is a price guide for wrestling cards now, here's a link to where you can buy it:
The Wrestling Card Price Guide | 2010 Premiere Edition
As with all printed guides, it's really a matter of what people are willing to pay, but the guide is worthwhile to look at and own.
*And no, I am not associated with the guide in any way other than I bought one and happen to talk with the guy that made it once in awhile*