That's like asking "how much is a car?"
The marquee company will want to know before quoting:
Size - though they will advise the size required if you let them know the number of guests, whether it's for a sit-down meal, whether tere will be music and dancing etc.
Terrain - what is the ground like on which the marquee is to be erected and what is access like?
Furniture - what will be required in the way of furniture, staging etc?
Accessories - will you require flooring, lighting, heating, air conditioning, draped lining etc?
Date - the cost will vary according to when you wish to hire the marquee. You could expect June and July to be the busist, and therefore the costliest, period.
I'm sure I'm not alone in finding it strange that you have an aversion to giving your email address to bona fide businesses, but any company will be happy to discuss the matter with you over the telephone.