I've had Prime since it first became available. I think that was about 10 years ago but I'm not sure. When I got it the only benefit was free shipping. I live in a town of 3,000 and I don't have a car so I was doing most of my buying online and shipping was a significant expense. Prime then was $80 a year but it probably saved me between 2 and 4 times that much, although I never really calculated it.
Of course from that time on the bulk of my purchases were from Amazon. Before that I bought from a lot of different online places. And I'm sure that's what Prime is all about for Amazon. My guess is that it makes them a lot of money while saving me money.
I also watch the videos more and more and today they might even be enough to justify the cost of Prime. I don't own a TV because commercials ruin the mood of shows I like. I do have Netflix and I watch it more than Prime TV but I watch Prime TV shows and movies a lot too.
For me it's a great deal. By the way, living in a retirement home I also buy a lot of stuff for my neighbors. It's all tax free and mostly shipping free and it saves them a bunch too. And it gets me an occasional free home-cooked meal.
Barry