Here is a complete list of all of the materials used to build the Countertop Incubator. Downloadable csv is HERE. Altogether, the whol project cost over $80USD and it could have been much more than that if I had to buy everything new. Most of the parts that were used, I already had. This simple fact informed many of my design choices, yet didn't really feel like a constraint. Since I was doing this whole project without any hope for optimization for mass production, shaving all my costs to their very smallest wasn't the prime motivation. Mostly, I just wanted my girlfriend to end up with a working tempeh incubator, that could fit on a coutnertop. Goal achieved!
The heated bed is the largest piece, and what set a lower limit to the size of the device. If anyone else wants to build an incubator, you could certainly get a different heated bed and power unit. I believe that both of mine are oversized for what they need to be, but (again) I wasn't trying to optimize too much. One other noteworthy part is the heated bed controller. Frankly, I didn't want to bother with making my own solution to controlling a heated bed, when the good people who design open-source 3D printers with RepRap had already done all that work. Buying the heated bed controller (as well as using the Arduino) are the two largest indicators that this is a hobby project, rather than a buisness venture. These choices also keep the design from being the 'fabbiest' thing around. Certainly much less 'fabby' than GaudiLab's Incubator Controller or the Biodesign DIY Incubator. However, my version has the controller, power supply and heater all intgrated into one device that could work in a home kitchen. [And, really? Can't the end justify the means?]