why do u think you need 18v?
I don't think it needs it. I just always find I'm utilising the extra headroom that the pog offers, specifically with the sub octave, and that other sub octave pedals where never that interesting to me as a result of only running at 9v. However, as erskin points out, that's comparing octave pedals, and not a sub octave fuzz, which I'm sure will be punchy enough for what it does.
Plus at higher gigging volumes I guess most people aren't going to push sub-octaves very high incase they mess their speakers so then 18v is going to be a rather pointless thing to have just to satisfy bedroom players like myself