The quality doesn't look particularly good to me. I have quite a bit of experience with prosthetic pieces (not stp's or penis prosthetics although I have made one in the past) It would not be particularly difficult to make something a whole lot more realistic than what is portrayed on that website. The hair piece is simply awful and the tint used in the product is far too uniform.
edit, after reading a few of the responses in this thread, I looked at the "reelmagic" appliance. It looks much better, the tint, flocking, wash and paint finish is much better, and the sculpture/cast itself is far more realistic in form. The price is quite intimidating though at just under $900 USD. I'm going to look into this a bit further and do some pricing, I'm convinced a trade off is possible between the price and quality. I may start a thread soon about this topic if there is anyone interested.
another edit, I managed to dig up an an old photo of one that I made a few years back, not this is NOT an stp, it was a super cheap rubber willie (I sculpted to look diseased) I made for a low budget short film that required a gag involving peeing blood ( dont ask...) in the end it was never used because the producers found that it wasn't legal to show someone urinating or something like that anyway, this was made for a cost of about $8usd (1% of the reelmagic price lol) and took about a day to fabricate.
IF anyone wants, I could write a tutorial on how to go about making something like this (only better) or I can look into producing a run of photo-realistic ones.