We try to be fair with everyone who purchases each item. When you buy the item you are buying two things.
First you are buying the secret, and the item or prop. Item or prop is just the bonus.
Once you learn the secret or principal behind the effect that cannot be erased. The creators have spent years testing, using and then marketing these effects.
It would not be fair to other magicians or performers to be able to buy it just to see how it works.
Second, each item has a good write up description, as well as many have video demos so you can see it performed in use.
So you should have a good amount of information at hand before you make your purchase.