$39.95 per snap may be a great price and I'd buy them in big quantity if without the limit of "3 allowed changes per snap".
In few words, suppose to snap a domain renewed at the last moment by its owner then you put it under a second domain which's registered by a competitor and you play your third and final chance on another domain that, after several months, isn't released ... What now ? You've just lost your snap for nothing
Honestly, I bought 15 snaps on Snaps.com but I'm not quite sure to buy others at these conditions, just my opinion, it remains an excellent service even if with some bad limitations ;-(