Ghost of tsushima sold for 60$ for almost the entirety of its first year and got sales in holidays to 40$. The game had a strong launch, was released polished and had with a score of 80+ on websites.
On the other hand, Days gone price went on sale for 40$ around 3 times during its first 6 months and was permanently dropped to 40$ for 2020. It was also frequently going on sale for 20$ during 2020. Getting launched as buggy as it did, didn't help it in any way. It had a 71 rating in metacritic and was bashed in most websites.

You can't compare both just based on unit sales. You have to take in consideration ROI, net profit and other things to make a direct comparison. As it stands right now with the information we currently have, the only reason days gone got to 8 million is because of the price drops. Dropping to 40$ and 20$ in the first 12 months doesn't look good to the public and investors and doesn't really help build up hype for a sequel.

Finally, do we even know when did days gone hit the 5 million milestone? Ghost of tsushima hit that milestone in Nov 2020. So many unknown variables needed to discuss the success of days gone compared to other PlayStation first parties.

We live in a stupid era of gaming. On one hand, 800K of SMTV is a massive success. 8 million of this game is a failure to Sony. While this is more of a reason why I think Meta is a cancer and should be abolished. (tho DG seemed like the most mediocre generic game out there) but Meta is more harmful than anything. A lot of good games suffer in sales because of a stupid number. Then we have other AAA devs saying certain games that sold in the millions were a sales failure.

Kill Metacritic as it's a useless site.
Publishers need to not dump so much money into one game. How we get Anthems and Avengers. Put some of that into smaller projects and then 1 million will be a success. Not saying you can't have larger projects but they don't need the inflated budgets they often do have.

Tsushima: Acclaimed by the “media” and by fans, 2nd game with most GOTY awards only behind to the all time record, the last of us part II.
Released an extra paid DLC and a Directors Cut Version. A movie is in the works.

Days Gone: Bashed by the media and “fans”, no extra DLC, no PS5 version. Spent more time on sale than Tsushima has been in the same timeframe (mostly because the bashing). Released with a lot of bugs and way less polished than Tsushima.

Despite some people on this site saying that Sony games barely made any profit, most of their PS4/PS5 games already made plenty of it.

Well, there can be reasons why good sales don't equal good success (depending on the definition of success). At least I am happy to see a lot of gamers enjoyed the game after the initial bugs were ironed out.

But I would add another take, just my personal opinion: I think Days Gone probably deserves a sequel more than Ghost of Tsushima. There are some reasons for it. For one: GoT is a great game without a doubt. This is a reason, because it is much harder to improve on an already good game. There is a big chance a sequel might just fall short and tarnish the reputation of the franchise. A mediocre game with good roots on the other hand might be refined into a gem with a sequel.

Also a very subjective view, but mine: I feel like GoT is more samey with other Sony games. That is nothing bad in itself, it is just that a lot of Sony games are big, cinematic, narrative driven and visually pleasing action adventures. The details may differ, so they all have their place, but as I feel it God of War, Last of Us, Horizon Zero Dawn and Ghost of Tsushima all are tapping into a similar market. Days Gone feels more sandboxy, more systemic driven. Giving that series a sequel would help Sony to diversify their lineup.

As I said, my take is very subjective, so you all probably disagree, but it is just my opinion.

One was on sale for peanuts, unlikely it made much money.

Even if Days Gone made enough money, we don't know how the sequel was actually pitched, which is also something to consider. Besides it's not like Sony is closing the studio. They are making a new open world game and they definitely use some of the tech and experience they got while making Days Gone.

The launch was very rough, it had too many bugs and glitches and due to it releasing at the wrong time reviews also where not that great. So the game wint get a sequel and isn't totally comparable to Ghost of Tsushima. Luckily the game is getting a somewhat cult classic treatment from fans, same way as driveclub and it sold very well. So in the end it's a success. But the launch should have been way better and for that Bend can only look itself in the mirror, unfinished products shouldn't be the norm and Sony was rightfully disappointed, it's not like they didn't have the budget and in general Sony isn't one who makes a big fuzz about delaying games.

I think Days Gone with all circumstances included deserves now a chance of a sequel to rectify the mistakes done with the 1st one at launch.

Not really apples to apples.

Even your source in OP say the LOCAL STUDIO MANAGEMENT was disappointed, Sony management never said anything about the title. And whoever gave the rumor of the sequel pitch being denied wasn't Sony central making it public.

And truth be told, neither GoT nor DG needs a sequel their story was self contained so I'm good with both studios making a new IP.

Also as people pointed out, the Directors Cut, the Legend and the DLC for GoT plus it being well received by midia, fans and alike all put it in a very different situation from DG (which I liked a lot, even with the moronic bike mechanics, and technically GoT is much superior). So really it isn't a surprise why one is better viewed then the other, besides DG was a bet from Bend to enter AAA on console space (they were doing spin off on PSVita before that and their last great IP before DG was ways back) while Sucker Punch have been receiving constant good reveal and results, so let's say Sony have more confidence.

8 million should be enough for a sequel tbh. That's one hell of a playerbase. Even if half bought it at full or near full price for the sequel...

I'm sure at the time of launch it may not have seemed like a good idea but damn...

Imagine not releasing a new mass effect because of andromeda?

Surprisingly good sales for Days gone but i wonder if Sony were happy with the profits, i remember some some guy from the dev team bitching that too many people were buying it after a price cut and that if fans wanted a sequel it was important they bought the game near release it at full price.