It does become more affordable, but not like it once did. 

Yeah, but that's the thing. You'd think that the cheapest options would be slightly higher than that old price for the cheapest models now, but I can't find a new PS4 for less than 299€. That's quite a difference even with inflation and added price for extra features.

Although nothing is impossible, doing it would require perfect and perfectly timed strategy, a lot of luck and a lot of efforts, resources and money most probably not worth the result and surely best spent on PS5.

The only way: Sony slashes the price. PS4 for $150 and pro for $250. Sony doesn't do that.

Yup. If they ever do that, it will be in the last year or so of the PS4's retail availability. But it won't likely ever get a permanent price cut that low. I don't see the PS4 Slim below $200 or the PS4 Pro below $300.

Won't come even close, as that requires PS4 to sell some 13 million more consoles in other territories to offset the massive deficit in Japan (assuming PS4 hits 10 million there). It also requires a very slow PS5 start, a much bigger price gap, and no backwards compatibility.

A perminant pricedrop to $150 might help it exceed 140 million, but 157~ million ain't happening.

That's the thing, it makes no sense to focus on trying to push maximum lifetime sales of a system you're about to replace. Not when you can spend those resources and money on the new system that represents your future for the next 7 years. 

Sony have the perfect storm in 2013. First, abandoned the Ps Vita for pursuit the strong point, stationary consoles. Second, the solid launch of PS4, only with minor problems all big videogame launch have. Third, Nintendo and Microsoft have big problems with the successors: Nintendo has two times: 3ds and Wiiu. Microsoft has disastrous e3, sony counters in the same E3. Now, Nintendo Switch is a leading platform, and have the same price point than regular Ps4. If sony reduced 50-100 for Ps4, Switch has the end of prices with low price point with lite and end with regular Switch.   It's a different spectrum of consumers but exists a big overlap(all three equipment is a dedicated game machine), for too many people, are good enough.  

The big price drop to regular PS4 to $150 is too risky and may bleed sony financial good status. Launch a new console and big price drop, at same time, is too risky. 

Sony also wants brand power like Apple and Nintendo. Cutting the price permanently makes consumers perceive it as inferior and a weaker product. A $199 base PS4 would lead consumers to expect $99 Black Friday deals.

It's not going to happen, the PS2 sales were extremely inflated by the fact that the PS3 had a disastrous launch selling at 600$, so many people in regions primarily dominated by Playstation and beyond decided to go for the much cheaper PS2 which was still getting good multi-plat support after the PS3 launched, it doesn't seem like PS5 is going to do anything crazy like the PS3 and will launch at a more affordable price( With Regards To Inflation), so it doesn't seem like the many people will settle getting just a PS4 when a PS5 likely won't be much more expensive once it launches.

Another reason is that PS4 isn't anywhere near as dominant as the PS2 was before in certain regions, Japan's gaming landscape over the past 20 years has completely changed with many moving to mobile devices with dedicated home consoles becoming very niche in that region, during the PS2 era console gaming in Japan was still somewhat relevant, now it's very niche. PS4 will likely end up with 10M sold in Japan compared to the PS2's 23M

Even in NA, while the PS4 is still certainly selling very well over there, I still have find it unlikely that PS4 will be as dominant in NA as the PS2 was before, and I think it's cause of increased competition in NA. Back in the PS2 era, to most people the PS2 was legitimately the only console Americans went to for 3rd Party Support, the Gamecube wasn't getting much and while the OG Xbox was getting 3rd Party Support, it was Microsoft's first console so developers and consumers weren't really as willing to try an Xbox over a trusted name brand like Playstation. The PS4 however is dealing with far more competition in NA with Xbox being big primarily in NA and many are likely choosing an Xbox One over the PS4, which is the reason why I dont think PS4 will have the same success sales wise in NA as the PS2 had.