I deal in ephemera in general, not stamps specifically. I've had this Brady CDV of actor Edwin Booth - John Wilkes Booth's brother - for at least 20 years. I only recently learned of early pre-cancels with cross or single slash cancelations. I realize that the R13c is a common stamp, but I was wondering if a pre-canceled example still attached to the original photo has any premium value. I also have another CDV with an R11c 2c Playing Cards used on a photo. Is that anything special ? Check photos.
Generally the value is set by the highest valued facet of an item when it hits multiple areas of interest.
As to the revenue collector, the stamp's value on a generic or fungible photo is the "normal" price which is higher than if the stamp was not attached to an item.
The fact it may be attached to a higher valued than generic photo does not change what the stamp is, it merely makes the overall usage more attractive to a revenue collector. A knowledge collector would know to allow a higher price due to "more value" provided by other points of interest.
For you as the seller, it really doesn't change your price much, rather it broadens you base for potential buyers.
Do you know if the image is from Booth's personal life or if it is from a play? Edwin Booth was one of the most famous actors of his time. Today his reputation is overshadowed by his brother's infamy. In any event it has both historical interest and artistic interest as it is from a photo by Mathew Brady.