There is a brilliant little book where the author details exactly how she set up and now runs her veg box scheme, with pricings, sowing times and so on. Of course just because I have tried to find it, I can't
I even have a spare copy....... I will come across it soon and I'll let you know - the detail makes it worth a read.
I decided a while back that I wasn't prepared to slog so hard growing veggies for people who couldn't be bothered to put in the hard work themselves, so now I mainly grow just for us and our family, with the occasional surplus sold in our 'eggs for sale' box.