Looks like the guy that sold you the LR hooked you up bigtime!
My LFS charges 20 bucks or so for mushroom corals like that one.
I'm new to the hobby, and I keep buying LR from the LFS that isn't in the usual LR tank, but in other tanks with fish. After they've pulled it out of the tank, they usually don't care if it's got a few small growths on it. Free frags, fantastic!