I've had Amazon Prime since it began when it was only free shipping. I live in a rural area and I no longer drive so it was a big money saver for me.
Then they added video and that was a big plus for me. I also have Youtube and since I like old movies and TV shows I doubt I'd have signed up for Prime if the free shipping didn't interest me. But I soon realized I was watching a lot of good stuff on Prime Video that wasn't previously available to me. I don't own a TV and haven't for most of my life so my experience in this isn't typical. I also have Netflix and i think I probably watch 3 or 4 Prime TV shows for every Netflix show I watch. They seem to have a better handle on my taste.
I have a library full of books so Prime books didn't interest me much. I've used it a time or two. Kindle Unlimited didn't interest me either but then I got 6 months free with my new Paperwhite. I didn't even bother to check it out for a couple of month and when I did one day when I was in the mood for a legal thriller and none in my library seemed to fit my mood. I checked out a Kindle Unlimited book by an author I'd never heard of and gave it a try and it was excellent. I never would have paid the $10 price for that book, being by an unknown author, and I would have missed a really good book. My free 6 months has long expired but I've kept it just for trying out strange new authors. I can't say it pays for itself. I don't think it does in my case. But I do get a extra good book now and then that I'd have missed without it.
I don't need KU because of the size of my library. I've been buying books when they go on sale for years, usually for $2, and I have a lot of them now. But I'd miss it and I have no plan to get rid of it.
Barry