I bought a serrated Renegade off the 'bay for about that price. It's a nice knife, the sort of quality you'd expect from a Spyderco, but not my favorite. The bowie blade is just a bit too much for me. I don't think the resale value would be much (if any) more than you'd pay for it. I've seen Renegades sell anywhere in the $40-$70 range, depending on the blade configuration. PE's seem to be the most valued, partially serrated to be the least, and SE's somewhere in between, generally speaking. I think the knife was originally conceived to appeal to biker types. The fully serrated is interesting in the fact that it's more of a scalloped edge than serrated. I'm not sure if any other Spydercos were produced with this type of edge.
If the knife appeals to you, then by all means, buy one. That's a pretty decent price. However, I wouldn't look to them as an investment opportunity. I could be wrong though, of course.