This GPL script is meant to get order of magnitude estimates of reprap economics; to answer questions like how long would it take to make a boat with a reprap? Would it cost less than buying one?

To use the script, put in your estimates for the use of a reprap and click the 'Account' button. The numbers in the reprap economics script pop up menus are rough, round estimates. The values for future repraps are pure speculation.

According to this script, to make stuff cheap you have to make it quickly.