[agracier]

I think it is just a way of assuring that these skins are at the beginning of a list. When you go to choose a skin other than default, these will appear first if they have a $ at the beginning of the filename. If you have a few hundred skins for one aircraft type, this can save a lot of scrolling and searching.

I often use an exclamation point '!' in front of a filename when i want a directory or a particular file to be first in a listing.