My friend's LFS....we have about 50 of them in currently...and just $12 each (or half that during sales). That particular specimen is a full 12cm across (my hands are large-ish, so it can be difficult to tell).
Try aquabid.com for some Pomcea Bridgessi. That's what I have and they get about 2-3 inches. Make sure they're Bridgessi and not Cana's. You can tell because Bridgs will have the spiral of their shell extending while Canas have the spiral mostly flat.
True, but so do 'canas', giant ramshorns, and many other species...'applesnail' is a very large umbrella....it pays to be able to identify the most common species available.