I agree, the $25 / month approach definitely seems weird.
I see a lot of reasons for Andrew wanting to charge. People countlessly complain on here about the quality of transcripts. That could be remedied if he had more money coming in. Charging might also support the b/w costs. Not sure how much he has been taking in via the ads in the beginning of his videos.
I have to wonder if there is a better solution for what he is trying to accomplish. To me, part of the problem with making Mixergy throw off cash probably stems from the fact that right now the audience is kind of narrow. It targets scrappy people involved in startups. Advertising probably wont yield much on that end.
Maybe the goal should be to actually expand Mixergy's audience to a wider audience to create more advertising opportunities. I wonder if Andrew has ever considered trying to offer his programming on one of the bigger tech sites. Some kind of deal there could work and he has a good library of content built up.