I'd say about $15 on the low to shoot a large magazine of .223 full auto... up to $50 for a belt fed 50 cal machine gun... something like that... just depends on the vendor and what weapon. Bolt Action 50 cals from $4 to $7 a shot. stuff like that...

My son wanted to shoot the M16 FAuto - $15 for 2 30 round mags. He shot one mag and I shot the other...