Calm down, Cindy - don't get your panties twisted.
The shims you linked look like they're designed for a Fender style neck, not a Taylor? I'm gonna presume the ones you picked up were appropriate, though
If you want to make them, though... easiest thing would be just with a decent, sharp hand plane. Work out your dimensions for whatever angle you want, grab a good set of calipers or (better yet) a dial indicator on a flat surface, and you can work out your slope from there. You're presumably going to be needing it very thin, so holding the piece down and supported is probably going to be your biggest issue.. Either work with a larger piece and then cut it to size afterwards, or grab some double-sided carpet tape and stick it down to something more substantial.. keep that tape as a complete surface underneath it - at that thin, your work piece will deform around any gaps in the thickness of that tape.
As for setting up shop selling them.. yeah you could make them for stupid cheap, so the majority of it basically comes down to the 'surround' costs of handling, managing sales and enquiries and all that crap...
If you already have all that infrastructure setup for more expensive items like StewMac does, then it's plausible - but as a dedicated 'product', I think it'd be more of a headache than it'd be worth.