The floor price for 2TB SSD is basically stuck on USD100.00 for reputable brands. Less reputable brands are significantly cheaper but the good ones are self-policing around the floor price.
People like Tom's Hardware say "oh its the NAND shortage" but thats bullshit. It's the last vestige of not-really-illegal collusive pricing behaviour by a bunch of highly profitable manufacturers.
Demand (price) is driving this. Cost has nothing to do with it. "it's the market" is true, because if somebody dropped the floor to USD80 or USD70 I am willing to bet they'd make a killing for a very short while until the others come on board but while they can make book on $100 they're not going lower.
the other SSD sources are very dodgy. There's a lot of risk in going for the super cheap brands right now, you only have to read the reviews to see they come up far more often in post-purchase failure and inevitably problems with replacement. Not to say the majors never fail, but nobody much complains about their RMA on the failure.
Pricing of 2.5" HDD are now predominantly driven by SMR or not SMR as far as I can see it. Shucking is no longer much use to anyone. I expect some of the shuckable drives to migrate slowly to SSD and not bother saying so except indirectly "shockproof" or somesuch. It would actually be better for them not to admit they used SSD, than have to break the de-facto price barriers here.
If you want 4TB or higher, you are paying a premium, its more than 2x the cost of 2TB. The unit price of a 1TB does seem a bit more malleable and the sub TB units are now cheap as .. chips. You burn PCI lines or USB ports to glue these into RAID structures. Nice if you have the slots. Highly reliable with all those discrete media units but you need loads of them to get back to the 5-10TB scale effective filestore size. DO NOT USE USB MEDIA IN RAID IF YOU CAN AFFORD NOT TO
(I don't think M.2 or SATA 2.5" FF has much to do with this)