I see no reason to think that the cover is philatelic in nature. There is a Fred C Rollman born in 1858 listed in the New York Public Library's Photography Collection. Mailed photographs could account for the triple rate if it is the same person.
There are at least 5 collectors in this thread who would bid this cover up to the levels being discussed here, and there are certainly others out there. I don't know what you have been putting up on
ebay, but apparently none were covers equal to this one.