I'm not sure what you're talking about here... MLB is offering the exact same monthly pricing within the app as it is outside the app: $24.99.
The $124.99 for the full season is available from the website only.
Regarding blackouts, MLB has been working on that for a few years but the local cable companies won't sign off. The other commenters are right, MLB has been at the forefront of online broadcasting for many years -- MLB.tv was one of the first online broadcasting services.
I didn't realize there was a monthly option outside the app. I've always just bought the full season package.
Good for them, then. I guess they realize the revenue sharing with Apple will more than be made up for by the increase in volume of monthly subscribers this drives. Like I said, MLB has some foresight and intelligence in this area.