Hmmm. Not aware of anyone else in the "We cut, you sew" business. Probably a good reason for that. Many people have observed the price of a complete Sailrite kit is not that far below what, say, F/X or SailWarehouse charge for a finished sail.
There's a reason for that, too. The materials costs are pretty much fixed. There's a lot of design work, cutting, and marking hems that goes on. In a way, the sewing is the easy part. Sailrite (or any modern loft) has that big flatbed plotter/cutter to pay for, & the expensive software that drives it.
So if you really want to make your own sails AND save money, shop around for a good price on sailcloth -- it's mostly Contender or Challenger anyhow -- and do the designing and cutting yourself. It is not terribly hard, if you are handy with a metric tape measure. There's a nifty freeeware program out there called Sailcut CAD that will let you design a perfectly good sail, then spit out plotter coordinates accurate to the thousandth of a mm.
Then it's down to you, a tape measure, and a hotknife.
I've built three sails this way, and they are really nice sails. Second and third better than the first, of course -- there is
a learning curve. I will say this: after you've done the hard work of designing, laying out and cutting your own sail, you'll realize Sailrite's kit prices are pretty reasonable. Takes us about a day to lay out and cut; half a day to sew the panels; and most of two days for the finish work (boltrope/hanks/slugs, leech lines, batten pockets, corner reinforcements & grommets, reef points, etc.)
Scratch building is an option if you understand basic sail theory, enjoy that sort of thing, and place no value on your time. Your final costs will be ~60% of a Sailrite kit, maybe 25-30% North Sails or local loft. No one to complain to if it doesn't fit, tho.