Maybe it's just me, but I cringe when I see something like that listed as a "bowl" blank... very few bowls can be made with a blank that's a mere 2" thick. Saucers, yes, but bowls? Even with a faceplate glued to it, you still end up with a shallow cup.
Those blanks are better listed as bottle stopper (or pen) blanks. The bigger blanks are in the $20-25 range from most places, probably $15(ish) for the smaller one. So your price isn't out of line, if you're competing with the brick and mortar stores...