The skirts on ebay are indeed rare items. Only the convertibles, Virginian hardtops and some Vagabonds got them from new. It seems that most have disappeared from original cars making NOS or very good used ones very scarce. A decent set with the trim can easily command $1000 or more...and I've personally witnessed that happen at recent national meets. So, if you're looking for skirts and have the bucks to spend, you won't lose money.
It is important to note, however, that there is an installation kit that needs to be installed on the car body to take the skirts. I have the mounting instructions and it details the items needed...all of which can be fabricated by anyone with shop tools.