I mean, my personal opinion would be $5, but that's because I view the patreon $10 as $5 towards making it and $5 towards actually getting it. Most magazines that are $10 have around 100 pages of info, with 10% being ads. Currently, the ezines have less than that, but I also don't know the equivalent cost in time, effort, and material that goes into them so I could very easily be wrong.
But regardless, it should be a feasible enough price that 1.)it makes sense and 2.)it is appetizing enough that those who don't want to pay a monthly patreon, or who want to cherry pick issues, can do it without wondering "should I just get the patreon?" I mean, that said, if you are an extremely patient person, you could annually, or semiannually, just pay $20 for one month and get access to everything that came before.