I would say next to nothing. One, personalized is generally always worth less than an unpersonalized signed photo. A guy named Mike doesn't want to explain to everyone why he has a picture signed and inscribed to lets say a "Mary" hanging on his wall...unless that's his wife's name. Secondly, if you can barely make out the signature because its so faded, then why would you want to spend any money on it as it will only continue to fade away until their is nothing to see other than maybe an indentation to where the marker met the photo.
A collector, even a beginner would want to spend a few extra dollars getting something a little more visible to see.
Remember, value depends on many factors. The collectability of ones signature is based on supply and demand, along with the medium in which its signed onto and if its personalized followed by its condition.
Lastly, current market values; I personally think the market is down now as compared to the same time 10 years ago. With the passing of Neil Armstrong in 2012, along with several other astronauts of the era and Apollo technical support personnel, the interest seems to be sagging a little. There is some popup moments in the market with documentaries and a few celebrations to highlight the 50th anniversary of the moon landing that excite interest which reflects on the market in collecting, but I think the 40th anniversary 10 years ago was the peak of collectors market in value of such things as autographs.
Additionally with the passing of some big time collectors, a lot more things are coming to the market or flooding which will also influence and drive down items that once were commanding high pricing. Go onto eBay (yes not the most trusted source) and you will see an number of inscribed N. Armstrong WSS lithos with strong bold signatures and personalized for anywhere between $1,200 - $2,500.
Just my two cents.