YES! People do collect them!

Take a look on ebay. After you search 'handkerchief' in VINTAGE, then use the menu along the left side, and click "SHOW ONLY SOLD LISTINGS."

Some sold for $4 per, others a bit more, a bit less.

If you plan to sell them, I think you need to keep them as they are, not framed or anything. If you plan to keep them, THEN you can frame them, or use them in the other ways mentioned.