The best solution I have found is the modified Detolf display case - just completed my second one this week. With welding, paint and extra glass they still average under $150 each and store 30-40 planes. It's also pretty compact. Not my ideal solution but it keeps most of the dust off and little prop-spinning fingers away.
I have checked out a few used office furniture places around my house and have yet to find anything that is acceptable - usually too commercial looking.
My dream case is this merchandise display case at the local Audi dealership I call on. It would be perfect for my collection and it has halogen lighting (easily a $3K unit). I keep telling my retailer that I want the case and that if they ever go to get rid of it to call me first. One can always dream....