Not 100% definite on costs yet, but as a rough guide half the price of a Lastolite one, but probably less....
So you're not buying a lastolite one? What one are you getting?
The 8'x7'box is very big (my friend has one) and you need decent ceiling height to use effectively - a great box but also certainly needs two lights to get any sotr of even light. It's pretty easy to setup with some space in the room but can be pretty difficult to get down!
I use the 6x7 hilite. This is the best size imo. Turn it one way for portraits of up to two or three people and then the other for widergroups up to about 5 or 6.
The 7' height is just enough in most standard living rooms for standing portraits of people - even those over 6'! i have the vinyl train too and although it shows up pretty grey, it's about a 20 second job to make it white with some shadow detail remaining
Turning it so you have the 7' width, you can squeeze a family of around 6 people into it. You will probably have some other areas to clean up but that's usually a quick job.
Any smaller and you are restricted a lot more. The small ones though are great though for on location head and shoulder or 3/4 portraits.
The hilite is a fabulous bit of kit. i also use the black bottletop which is a superb addition for a nice black background.
Also I can easily get a nice grey background by not adding too much light to it. All in all a great buy.
Takes me about 2 minutes to set up and the same to take down. Some people have difficulty folding it but once you get it, it can be folded in 10 seconds.
Good luck
JD