I don't count ammo cost really, always cheaper to buy away from the site. Especially if you run a machine gun!
I like Awa herts. The walk on has gone up to £30, but with that we have also seen site development. Plus you can't play all the areas in one day so there's a bit of variety. Another place is £25 but you know you will bee playing up and down or across the site. I'd rather spend the extra fiver.
You can get a burger at lunch if you want or bring food. But as far a walk on fee goes I'm good with that all day long.