Burlap and adhesive spray to cover the panels. Easy as pie.
comon foam looks cool and it obviously works.
It obviously works for applications that require absorption of high frequencies. That is NOT what a home studio needs. But go ahead and waste your money because it looks cool.
As far as fabric on a budget... I read the easiest cost effective way is to just get the lowest count bed sheets from walmart.. I can almost guess most people here will be against this? One reason would be it isnt stiff enough to get a tight fit? I dunno.... Theres a local walmart that has a fabric department still so i can still see what they have too....
But have you seen any instructions on how to wrap the panels and keep the fabric tight?
I've got a thread in here somewhere that explains how I put fabric on my 703. Basically use spray-on adhesive. I have always recommended getting your fabric from the bargain bin at the walmart fabric dept. Get the cheapest that you can blow through easily. You can make your own panels very inexpensively.
HOWEVER, considering your unique space, you should seriously think of spending your money on a really good pair of headphones and do just enough treatment to get good vocal tracks. Something to think about, anyways.
It's just for suckers who want to waste their money huh? lol