If you really think about it, anything that is not "mass produced" is going to be more expensive.

The "production line" model of manufacture helps, but mostly where the quantities of what is produced is so large that the end cost of each item is significantly reduced.
Many also have spoken regarding the "cheap" labor that is being used in most of the garment industry (both good and bad), and both the wage and the benefits add to the price of what is made in the US.

I suggest you make an X-Kilt, Buy good fabric (you don't want a cheap kilt do you?), log your time making the kilt, and multiply that by a reasonable wage. Your kilt will most likely be more than you would want to buy it for.

Professional seamstresses/kiltmakers will sew faster, but that skill also comes with a price.

All the products we buy, we would like to have "less expensive" than what we pay, that's just the nature of things.

If you make any crafts at all and try to sell them you will understand what I'm talking about.
Those that sell at Highland Games, craft faires, etc. make a profit, but if they accounted for many of the hours involved in their businesses, they really don't make that much.