There's a couple of questions come up here, os:
£800 for the week is for a tent (it's approximate, nased on Abegavenny's pricing.
That may seem a bit expensive, but compare's reasonably well with a caravan pitch, or with booking peak season accommodation anywhere near the Eisteddfod site. The camp site is right next door to the Maes this year as well, which swayed us to glamping it as opposed to booking a cottage. The ability to pop in and out of the Maes is a biggy when you're there all week, especially with 2 (or possibly 4) children, and for us, it means that Cat would be able to get some rest during the day as well.
The glamping site will be close to the caravan and camping sites, and within the individual sites, you will be able to stay together (ie anyone caravaning can ask for pitches together, and campers can either ask for, or possibly just turn up and bag adjacent pitches). Anyone wanting to bootglamp will also be in adjacent tents. There was a 4 tent group in Abergavenny, and the tents were actually set up as a group of 4.
The Glamping facilities (kitchen, communal dining area, seating area etc) are only open to glampers, but if we have people staying in caravans or tents, I can't see a problem with arranging activities for us there - that's something I'd have to OK with Best of Wales, though.
And of course, any on or off-maes activities would be open to anyone, although depending on what was arranged, we would probably have to charge for things. I'm being deliberately vague here, because I've not planned anything beyond "being in the vicinity of the Eisteddfod for a week"!
BTW - Glamourous may be a slight exaggeration of the facilities: Although Glamping is coniderably more luxurious than camping at the eisteddfod, don;t think of the glamping here in the context of glamping elsewhere. Whilst "glamping holidays" basically give you a chalet made of canvas, these are very much tents with beds in, but they are tents that someone else sets up and takes down, and they are quite roomy, so considerably better than most tents!
There are no secure area for belongings, so I wouldn't suggest that you bring expensive laptops / sound systems etc to the tent. On the other hand, the whole area is fenced off and there are staff on site all the time, so if strangers turn up and start looking into tents, then they would get spotted and stopped.