The brs ones are I think $36 each. Plus a pump, but most everyone has a maxi jet 1200 laying around so you can one of those.
I have two of the phosban reactors and while they seem ok they arent really sturdy and the tops dont always line up just right and you get a leak.
I've heard not to run biopellets AND GFO so I will just be running the pellets. I don't wanna get my water too clean. lol
BRS sells the bio pellet screens that work in the phosban reactors, just keep in mind that the phosban reactors are kinda small so you might not be able to fit the recommended amount of bio pellets in it.