Here, let me break it down for you. 22ga Jena wire = $6.25/ft (if bought retail from a dealer, he probably gets it for less direct, or at least he should), Furutech 1/4" plug = $13.20 (again, retail). That's it, that's all of the parts that he uses. So if you figure that with braiding you get a 30% reduction in the length of the cable you'd need 14' of wire to make a 10' cable, and 4 of them for the type of cable he's making. So total that up and you'd need 14' x 4 = 56' total x $6.25 = $350. Add up the wire and connectors and I get a parts total of $363.20. For a 10' SE rewire he's charging $589. I'd say that ~$225 is a healthy margin for a pseudo-MOT and that's assuming he's not smart enough to negotiate at least some discount on the bits he's using. It wouldn't at all surprise me if he's able to knock 25-50% off the retail prices, I know I could without breaking a sweat. Then his margins start looking like $300+. Not bad for a job that takes a couple hours. And don't get me started on the $10/ft nylon multifilament. There's no way he's paying even $2/ft for that stuff.
Research ALO for more information.