Your fiance needs to toughen up

. We come from the great white north, and if we can handle the insane heat for 4 days (was only 3 days when he was there), then a Georgian should be able to take it with ease. I've never heard of someone leaving Bonnaroo, lol.
Definitely not too expensive either. Ticket is still one of the cheapest festivals ($230 compared to Coachella $320), and it includes camping (Coachella, add $40). And take this year for example, a Paul McCartney concert ticket is over $200 on it's own. Here you
get that, plus over 150 other bands! You don't have to love McCartney, that's just an example of the value.
You can bring you own food and booze for camping, so that's cheap (LOVE USA beer prices

). Once inside the main area, 16oz beers are $5-6, and meals are $5-10.
Some people might not like huge crowds though, I can understand that.
Wannee only has around 20,000 ppl, whereas Bonnaroo has 80,000-90,000. It's a goddamn pop-up instant city!