Santisa,
Hi, and welcome to the forum.
I collect both US and foreign stamps. Just over a year ago I purchased a large bag of old US stamps on
ebay for $29.00. It contained approximately 20,000 stamps including about 200 "Washington-Franklins" (the series that includes yours), some with higher denominations. I considered this to be a decent haul at about 6 stamps for a penny. As usual I didn't discover any stamp that cataloged at over $20.00, but there were over a hundred stamps that had a catalog value of just over $2.00.
If you contact the Mystic Stamp Co., they will send you a free US catalog that will benefit your quest.
Wishing you the best, whether you decide to collect postcards or stamps.
Sincerely,
Greg