Note well that several of the internet based sailmakers farm the work out to off shore lofts. This has the benefit of keeping labor costs low, and much of savings is passed on to you. However, there are several upsides to using a local loft:
they will generally come out to your boat and measure;
you have someone local to complain to when they are late delivering your sails (and they will be late);
they will often come out to the boat and install them for you, showing you how to use the various features of the sails;
and, if something is wrong with your sails (don't fit, rip, fall apart, etc.) they are right there.
When I replaced the sails on my 79 Oday 23 several years ago, I compared prices and features, and decided to go with a local sailmaker instead of Air Force Sails (an internet-based sailmaker; I don't know if they're still around). Although I paid a premium (about 30%), I think I got my money's worth. They came out and measured, talked to me about what features I wanted, delivered the sails to the boat, installed them, and came out on a sail to show me how to rig and get the best out of the new equipment. Since then, they have served as unpaid experts a few times when I needed some technical assistance, and have kept my sails in good shape.
I have read stories from many people who bought their sails on line. Most were satisfied, some were not. I have never read about someone who bought their sails locally who wasn't ultimately happy with the product. My humble opinion: buy local if you can.