As you're involved in organising a show already, I'm sure you can easily find costs yourself. It really depends on what venue you have, that alone can be anything from one thousand to 20 or more, toilets and first aid depends how many people you expect.
Attention Mods/admin Seriously I think you will legally find your not aloud to say the word Pikey let alone write it on a public forum as it’s an insult to the traveling community so can you please out of respect change it please. Regards