That price does not seem outrageous to me. You may want more than one if you have lots of stepping stones to make.
There are a lot of cheap concrete molds out there made of thin plastics. They sag when you put material in them or crack with much use at all.
Even with a good mold if you have an intricate shape you might want to build a box around and under it the height of your pour. Fill in the gaps between the walls of your mold and the box frame you make with spray foam or even concrete. This will keep the walls of the mold from sagging.
Whatever mold you choose, make sure you do not skimp and pay for a good mold release agent. And clean your mold up after each casting.
I assume you plan to cast them with a concrete mix? When you install them you will want to add a gravel and/or sand mix under them if they are only to be 1.5 inches thick.
Last edited by sdsester; 11-02-2011 at 09:09 AM.