I like this article from Antique Trader about the success of postcards at auction back in 2009 at the Lyn Knight gallery.
“A wide variety of Samuel L Schmucker postcards including full silk, silk inserts, projections and novelty postcards were sold at a strong steady pace. The Halloween postcards of Schmucker reached some record setting prices of $300 to $1,000 each.”
A silk postcard of the Million Dollar Pier in Atlantic City sold for $375, a black Americana advertising card sold for $275, and what I thought was most interesting was an HTL Santa dressed as Uncle Sam. That card sold for $1,100.