There's just...no reason at all to do it for business purposes. If you're a prepper or looking for a science project I can understand it, it's a cool project. But from a business perspective you can buy the same thing but better for dollars and have it the next day.
The lowest-cost options I know of for commercial custom chip fabrication are MOSIS and CMP. Their pricing starts at €650 for 0.35 μm, but it's true that the result is much better. However, turnaround time is measured in weeks. You seem to be suggesting that there are options that are one order of magnitude faster and two orders of magnitude cheaper (but perhaps with a much coarser feature size).
