Block Erupter , app to bit coin mineing

these things are blade asics , can handle 30 gigs/sec.they consume 200 watts. for incepting Bit coin traffic . Found 5 of them last night at good will ,checked them out on net then went back 2 hrs. later all gone. went back this morning and found 3 more at $6 each I snagged them . Did I buy door stops or can these things due more?