Well, I haven't built it yet, but I have done the research and pricing.

I intend to build a nice display cage (for my baby when she's an adult) at 42"Lx18"Wx12"H. It will be of high quality 3/4" plywood, waterbased stain and poly to protect, framed screen vents in the sides, 2 low watt florescent strips inside back for viewing, with a 3" substrate dam and bottom-hinged framed plexi door.

My calculations so far for materials and such, not to mention money spent on the tools, is around $90-$100 top end. Since I got most of the hardware free, that cut down on my costs by $10-20. That's just the cage itself, of course. Then there's supplies on top of that. I just bought an ultratherm heat pad from Rich for $22, and got her some large hides for about $8-10 each. The rest, such as dish and decor, I already have.

That's my plan... hope that helps even a little