I never suggested free, you're not going to invalidate the point by taking it to the extreme with a strawman.
You're also exaggerating the price differential here between pricing for games and movies. Considering that first run movies are 1 sale/person whereas a first run game can be sold as 1 copy for multiple people in a household; for a household of 4 to see a first run movie vs. playing a first run game isn't really all that different in pricing at all. If we're not talking first run, then there's all kinds of deals, sales, promotions and so forth that completely muddy the waters in terms of pricing on both sides, so its hardly as cut and dry as you try to make it.
And I didn't even say that $15/mo or $20/mo were bad in the first place. I just don't think they're necessarily the sweet spot for this kind of service.
it is very simple - you can both own and stream movies at several times lower price than games... from ownership part, Movies start at $20-30 and games start at $50-60... down to still $20 for Last of Us, vs bargain bin $2-$3 for DVD. Additionally PS3 is still $200, vs Roku, Chromecast, cheap BD player, that are all at least $100 less and usually more than that (built into TV for instance).
Then from technology perspective, you need 1x PS3 to stream 1x game... while you need 1x server to stream hundreds (if not more than a thousand) of movie streams (at least).
And the price is $12 for Netflix HD vs $15 for PSNow.
There is nothing muddy there at all. Pretty clear cut - it is a lot cheaper to buy/rent/stream movies than games, it was cheaper yesterday, it is cheaper today, will be cheaper tomorrow. It is also a lot cheaper to stream movies - hundred times cheaper.
So yeah, it is a good price. Might not be for you or me (i have both ps3 and ps4), but $15 per month is a good price regardless.