Did I read right? Do you have 50,000 covers of material like this? If so, $1,000 is not nearly enough. That would equate to five covers for a penny. You may have to work a bit an divide this into chunks the average collector can afford.
The last one scanned is the best that I can see. It would sell for at least $50.00 on
ebay. Those San Fransisco registered labels are hard to find. Most are stamped on with ink, not the stick on type that you have. You have another one shown and also one from New York. Linn's had an article on these within the last couple years that you may find interesting. I will see if I can find it. Someone else will probably find it before I even get home to look.
You also have some nice machine cancels.