Sorry, there is nothing all that reasonable about a "AAA" budget style game in this day and age, with gameplay that could seriously last you under 60 minutes to complete the entire thing, and charging anything more than $10 for that. Not by a longshot.
It may be a good game, great even, by MGS fan standards. But overpricing incredibly short games is certainly NOT a precedent that I think other companies need to be following. It is dangerous, yes, because they could all possibly see the $$$$$ flowing in, if people are willing to pay out the ass for a game that is honestly a fraction of what they would usually get from a $60 retail game. But it's one thing to pay $10 bucks for a classic-styled side-scroller, that you could conceivable speed-run through in an hour and a half or so, compared to a big, HD, 3D game whose story only lasts about an hour or less, and charging $20+ bucks for that.
It's about as bad as what Square pulled with FFIV: The After Years on WiiWare: they charged what would amount to a full DS game's price, for what should have been no more expensive than $10-$15, just because they wanted to fleece people by using the "download new chapters" model. They could have (and should have) just as easily released the entire game in one lump for $15, and that would have felt worth it. Paying $37 while having to wait months to finally have the entire game available, felt far less worth it, even though it WAS a fun game.
This Ground Zeroes model, to me, doesn't sound all that more appealing.