Yeah I think I paid $13 per polyp for mine. Only had them a month but the lfs I bought them from claims these are slow growers. Not sure if its a variety issue or not. I have heard both slow and fast but mostly slow growth for them.
In my experience they're slow growers, they're also considered "micro zoas" as they stay small. It seems now that I've got more than just a few of them they're growing faster. They're an awesome zoa.