How good of a carpenter are you and are you allowed to attach stuff to your walls? I've built tons of desks mounted directly to the walls with angled supports (so there are no desk legs getting in the way) and then built platforms around that. Sometimes I'll hang shelves from chains attached to the ceiling and stuff too.
All made out of sheets of laminate given to me or yanked out of the trash (think broken down Ikea stuff). Then I just buy some screws and 1x4's (for extra support and to give the screws something solid to bite into). I attach it all to the wall studs but if I can't for some reason (aluminum studs, drywall/plaster on concrete, etc...) I use evenly space plugs to attach the main mounting 2x4 (usually salvaged as well) then work around that.
I've made crazy set ups this way in some seemingly impossible spaces. Now however I can't really do that because my current space won't allow for it and I'm not quite as physically capable of that level of mayhem. The current set up is a couple old interior doors that I attached folding steel table legs to (with 1x4's for extra support and to give the screws something to bite into) and one folding desk with a resin top. The table legs were $20 a pair and the resin table was $40. I want to cover the door tables with sticky floor tiles so they are a cleanable high gloss surface (currently just enamel paint which isn't great but works).
Essentially I have three huge surfaces. The resin top is where my DAW lives. One of the door tables is on the abutting wall creating an L shaped work surface with the resin desk and has my Line6 head on it and I use it to put my laptop there so I can read manuals, the forum, lyrics etc (I keep copies of all that stuff on the laptop so I can just have Sonar in view on the big rig at all times). Eventually my mixer and when I need it my big keyboard will live there too. The other door desk is on the other side of the room and is basically a work table where I can work on my guitars and stuff but I also have my old DAW sitting on it so I can eventually fire it back up to transfer all my old projects to the new system. It might end up being where the laptop will live eventually too if I decide to leave my big keyboard set up all the time.
Long winded post is long winded but I'm taking a break from cleaning and figured it might give you some ideas. Cheers, Frosty.