One sees box lots of commercial bank covers at auction from time-to-time; they are probably most often purchase by dealers, who pull anything worth selling one-by-one and dump the rest into bargain boxes, where the covers might fetch anywhere from a quarter to a dollar.
But that dealer is working for that money; shlepping the boxes to a show, renting a table, spending the day entertaining the browsers, etc.
And
ebay would require that you scan each item, describe it, and ship it to someone ... who can them complain that you misdescribed the item. Unless you have exceptional material, would that activity be worthwhile for you?
How about scanning & posting a few of the covers here, along with a count of just how many you've got?
Cheers,
/s/ ikeyPikey