The perfect stone feels fantastic, cuts super fast, wears super slow, and is splash and go.
The difference in the price of stones can be any variation of things. Maker....Shapton's and Naniwa carry somewhat of a premium as they're considered premium stone's. They really deserve it too.
Other things like the ingredients....ceramics versus other abrasives, how thick they are, and simple marketing can affect the price as well.
At the end of the day, almost every stone I've tried worked. Some felt better than others, some cut faster, etc. I found the stone's that best suit me.