I've got a self-built stand for a 29. The frame is 2x4 construction with metal brackets for reinforcement - would probably hold 2-3+ 29 gallon tanks stacked up. It's much more sturdy than a typically fish stand and I can still move it around myself without trouble. Front and sides are sheathed in plywood. Finish trim around the top and bottom on the front and sides.
The back is open, but you could easily close it in if desired. The top supports all edges of the tank, but is not closed. The trim is setup so a thin (1/4") layer of foam can be used between the tank and the support, while remaining hidden from view.
The doors use a magnetic catch to hold them closed. One door has a very slight outward bend - I think installing a second at the bottom to hold the doors there as well would eliminate the slight bend (right door, lower left corner IIRC). Inside there is plywood across the bottom as well - adding more shelves wouldn't be hard.
The entire stand is coated in polyurethane to withstand incidental water (wouldn't survive a flood necessarily). Overall it's still in great shape.
Hard to pick a price knowing the time and materials that went into it. Looking at commercial stands, price range appears to be $60 for cardboard stands to $200+ for furniture grade. I'd take $80 and could possibly deliver to the MCA auction. Otherwise I could maybe offer pickup from Novi, as I'm occasionally out that way on some weekdays.
Here's from when I had it setup - stand looks essentially the same now:
