I just paid $150 for a like new (other than moderately dirty) G4 WITH a 48/3000 tank with 3 years left till hydro!
I cleaned it and lubed it and it dry fires perfectly with no leaks or bolt stick. It is loud but it has almost no kick. I almost didn't buy it cause its purple but my girl said she would play if I got it for her. I am working on a used G5 as my new main gun so I'll keep you posted but right now I am very happy, especially with what I paid for it.