Here's a box I built just for vegging. It's made out of a few pieces of very cheap particle board I had cut to desired dimensions at Home Depot with one piece of the wood I purchased. The dimensions were based on cutting out 6 sides from the big piece of wood I bought and are 14x14x25.
I don't remember the total cost of the box, but the parts used were:
-Wood(pre-cut at Home Depot)
-2 hinges
-About 4 Ft of 14 GA Outdoor lamp wire (don't really need 4 ft)
-1 AC Power Plug for wall socket
-3 PC fans
-1 Power Strip
-15W 1200MA AC/DC Converter for Fans
-Y-Adapters
-some Small chain to hang my lights from
-5/8" Brass hooks to suspend chain from ceiling
-Sockets for your CFLs
I don't remember the cost of everything, but I remember spending less than $40 total on everything. But you could cut some corners if you wanted, as you don't have to have a hinged door or lock. You could also do without the power strip and just run both power cords for your lights and power converter straight outside of the box.
You could also possibly use a regular in home fan if you have one handy, cut a big hole for that, and do away with the power converter and PC fans as well.
