I have project that I did and a offer was made to purchase it how can i determine the value and ask a fair price.
First, intrinsics: design time, labor time, materials, consumables, machine cost (machine time/depreciation), packaging, shipping, etc. What is everything you put into it worth? Second, extrinsics: what do similar projects of a similar quality typically sell for in the appropriate places? Then figure out if you need to compromise between those two positions and to what extent.