Chip,
Thanks for your post... nice to see a professional's inside view.
Going back and looking now, they do seem to be a little more expensive for the material.
As far as beach cats... there is a pic of a wave with a LP sail on the catsailor front page somewhere. The loads on a wave sail have to be fierce.

Although the labor to create the fabric is significant, the finishing part of the sail is a lot less than doing a radial cut sail.