With those software numbers, the number of PS4 games sold is around 1650 million units.
The PS4 has an attach ratio of about 14.1 games per console.

Is that the highest ratio for any console/handheld??

Not sure, but certainly is the highest SW sold ever on a console or handheld platform

PS4 vs Gameboy is coming right down to the wire. Will be very close either way.

I wouldn't say the pandemic killed it. It over 6 years old already when covid started in earnest, so it was already slowing down; as others have already said, once it was replaced Sony would rather people buy a PS5 than a PS4 so they opted not to take extraordinary measure to prolong the latter's life and just let it ride out what momentum it had left.

I would say that if they had done a pricecut the pandemic would have boosted the sales of PS4 even on the verge of death.

So yes the decision to let PS4 and X1 die was from their manufacturers, not fault of pandemic. The shortages of PS5 and Series can be partially faulted to pandemic thought.

Sony must've been making a lot of money on each PS4 sold at $300 by 2020, so they chose profits over sales numbers in the short term, then once PS5 was out the new system became their priority.

That would be my guess as well, they decided that whatever extra number they could sell with the system at 150 or 200 wouldn`t generate extra royalties from SW enough to justify it.

Sadly right now it wouldn't make sense anymore to make a PS4 SoC that allow to cut its price to cheap entry level system. Pandemic chip shortages and logistic problems really killed any plan to extend its life, unless economic recovery boost again chipmaking R&D and resources to levels allowing to make such SoC at a cost low enough to make the operation low-risk (older gen consoles, requiring much less computing power, are far easier to remake using emulation and cheap customisations of generic low-cost SoC, allowing Ninty, the most important company to make such replicas right now, to profit also on relatively low sales volumes, but probably PS4 power is still out of reach for the cheapest options).

If they're not going to produce many more PS4s they probably want to make sure they at least make a big profit margin on each one they do sell, hence keeping it at $300.

Well there's the super slim possibility, that the lack of PS4's is due to a new super slim model coming out. How it wouldn't have leaked by now seems impossible, but regardless this is pretty unlikely based on the shortage scenario. Any capacity SNY may have had lined up with TSMC for PS4 7nm APU's would likely be better diverted to PS5 APU's instead.

SNY has no choice but to take the long game into account, and because of that, even if they felt they could profit more off of PS4's right now, they had to make sure not to potentially let XB Series consoles get too much momentum. A weak start to a gen just causes bigger headaches that drags on, and SNY definitely remembers what it was like when they gave XB 360 a year head start. Since the XB Series consoles are proving stronger for MS than both XB1 and XB360, SNY has to keep PS5 at the forefront, even if that means sacrificing future PS4 sales.

Maybe something like this? The bottom one would be like PS2 Slim thin.