These are definitely sebae, I've looked them up on a couple websites as well as books before buying. There are two at the store but they are not a pair and are kept in different tanks. You're right on for price though. I paid 30 Cdn for him, probably about 45 US. He's a funny thing, swimming in kind of a wavy motion back and forth in front of the live rock.
There are no anemones in the tank, and I doubt that there will be in the future until I get another tank going. I just prefer the fish and whatever grows on my rock.