They're cheap as chips - £150-£200 depending on condition/model (marker only).
I picked up a G7 Fly Arsenal edition the other week - spent another £30 on a Spitfire board and now have a backup marker with all the 08 ramp modes, nice
PM phil-boy on here, I know he's going to have a black G7 up for sale this week (because it's sat in my back room at the moment!) and I think he may be looking to sell his 06 Speed as well.