I love the "cost" table. Having recently built a mobile phone out of a rotary phone (https://www.youtube.com/watch?v=fSkdWQswpc8), my costs look something like those, except:

Cost of materials: $50

Time cost: $1500

Then again, it is a prototype, which has to go with all the fixed costs, but to say that this cooker only cost $X isn't entirely accurate.