Okay, for the sake of conversation, I'll humor your guess that it will be 7 episodes*. The implication I got from their statement was that the game will be released over 3 or 4 years, as they make it. So is $50 twice a year really THAT much? The way I see it, SE gets their money to continue making a game, fans get a superior product that has has lots of time and resources invested into it, and no one has to pay a huge lump sum for one overly massive game. Everyone wins.
And for what it's worth, I DO think it's too early to be picking apart what little we've seen and start fanboy raging about how OMG IT'S NOT EXACTLY THE SAAAAAME. I've expressed displeasure at it being turned into an action game, but we all knew going in that was going to happen. Apart from that, I really can't criticize what we've seen because it looks gorgeous. Okay, I can criticize Wedge's voice because it's horrible, but everything else is great.
*I think they'll probably work this like Telltale does and you pay one fee up front and get to download it as it's released. Just because each installment is being treated as a separate game doesn't mean they'll charge you for it. It just means there's a lot of content because FFVII is a massive game, and it's going to be even more massive with updated graphics.