I bought a pre-cut 1930's repo DWR from Fons and Porter. I think it was worth the price and is going together very beautifully and quickly. I did not prewash. I also bought a pre-cut wreath wallhanging I'm anxious to get done before the holidays. Would consider buying pre-cuts again if it is the right price and design I wanted. A lot of the ones today are laser cut and curves are precut for easy placement.
As for precutting for someone else, I would probably charge too much!