Probably around $120 total (without the old mini fridge).. I'll get a couple pics of the mini-fridge I'm using to show the rest of the parts.
I bought a self-filling dog water bowl and an ultrasonic pond fogger to generate steam for humidity.
For the temperature, I'm using dual 60W light bulbs.
I installed a few computer fans to circulate air so that the temperature and humidity are homogenous, and an aquarium pump for a slow, steady supply of fresh oxygen to the enclosure. (I'll have to cut a hole in the seal to allow air to escape.. and to run wires through)