No, it's not worth it right now.
Defense soap is outrageously expensive (39.46 for a five pack on Amazon right now) with little to no evidence to support it is anymore more beneficial at reducing the risk of skin diseases/conditions following certain activities than other soaps that are much cheaper. If you look at their website under "Clinical Information" it only displays a letter from PetLabs Diagnostic Laboratories that appears to be from around 2006 to 2007.
It's odd it would be done at that laboratory to begin with (they primarily deal with animal testing it seems) but the study itself doesn't indicate specifically what may be causing the supposed effect (which oils exactly as opposed to just "defense soap"?), if it would really matter (since people aren't waiting 7 to 10 days to bathe), if it would have the same effect on human skin, on a human cut, etc. It also does nothing to compare defense soap vs. x (any other soap or common ingredients).
I don't really think a forum is the place to start getting into the intricacies of research (or at least I don't give a shit enough) but clearly one small "study" in approximately 2006 or 2007 with eight plates that didn't compare the product to anything else, which I'm guessing was funded by the company, with no reference to peer reviewed articles or reputable sources, and with no backing from reputable sources in the field of dermatology (for example) shouldn't lead one to believe spending that much money on soap is worth it.
My guess would be if you ask an expert (a dermatologist) they wouldn't think much of the product and don't be fooled, they ARE the experts, not a bunch of anecdotal reports or simplistic research.
I met a very highly regarded dermatologist in the field when there were concerns my friend might be developing Steven Johnsons Syndrome. I asked him if he ever heard of Defense Soap and his reply, like a previous poster, was it was a waste of money.
I'm not saying to believe me (since a lot of what I wrote is also anecdotal) but before shelling out that much money on soap (for a condition you're probably unlikely to get if you practice good hygiene) you're probably much better off meeting with a dermatologist, explaining what you do (jiu jitsu, wrestling, etc.), what they think of preventive measures, and if there's any recent research on the effectiveness of certain products over others.
Edit: If you find the evidence for tea tree oil to be convincing enough that you wish to buy it, which appears to be a common ingredient in Defense Soap, you can get it much cheaper online or most likely your local drug store.