Yes marquees aren't the cheap wedding venue people think they are! My brother and his wife borrowed a piece of land and the local gardening society's marquee thinking it would be a cheap way to have a wedding.
By the time they had hired flooring, dancefloor, generator, bar, tables, chairs, caterer, crockery/cutlery/glassware, portable toilets and all sorts of other things they hadn't thought about it cost them an absolute fortune, more than I'm paying for my wedding venue - and it took them 2 days to set up and a day to take it all down again! The catering was also a nightmare to organise because there was no on site kitchen.
The tipis do look lovely though - just make sure you've budgeted for everything before you commit.
Your catering sounds fab, I'm a massive curry fan so would be thrilled with the food at your wedding!