How many photos is 'too many' for a memoir?

I have found most publishers will determine the number of photograph pages in a book.

As noted, I'm sure that can be discussed with the publisher. However, if you're self-publishing, I think it depends on the context. I tend to love imagery, but if this is a family memoir, I'd say no more than one of each major family member, major being someone who takes up a significant word count, or a major player in the story. Spare us the full family tree especially if you're only mentioning someone briefly. Mom and Dad's wedding pic would count for both people, IMO. For a major person playing a large role at multiple times, one of this person at major life stages (such as grandpa in his WWII uniform, then again holding you when you were little, for ex) should do it.

However, there is no magic number. A recent good example of the right number for me is The Boys in the Boat by Daniel James Brown.

Irene, are you self-publishing or are you including photos in a submission to agents/publishers?

Is your 80k-word manuscript really only made up of 5 chapters? That sounds like some darn long chapters.