Out of 1000 consumers buying pci-ex drives, 990 are not performing workloads where it makes any meaningful difference.
Recently many manufacturers are replacing high-end components with chinese cheap stuff keeping the same name and price. Aside from some reliable products (Crucial T500, SK Hynix P41, Samsung 980 and 990Pro and a few others disks, mainly because these brands manufacture their own components), buying a Crucial MX500 is always a safe and smart move (it sounds like a promo, i'm sorry).
Oh I know that 99% of consumers will be served just fine by SATA SSD performance. My raised eyebrow was more that the MX500 is super old and significantly more expensive than newer, better NVMe SSDs today.
WD/Sandisk are like Samsung and Micron in that they are vertically intergrated and make the controller, the firmware, and the NAND themselves. The SN550, 570, and 580 have all been award-winning, fantastic value and even the old SN550 runs circles around the MX500. Today, an SN580 is about 30% cheaper than an MX500 and around 10x faster in sequential throughput, whilst also being around 50% faster in real-world application performance, which is significant enough to be noticeable even by non-technical buyers.
I honestly thought the MX500 was discontinued a couple of years ago, but if I'm wrong on that, then the higher price is likely either the economies of scale (fewer people are buying SATA, it's likely that orders of millions of units from big OEMs are all NVMe now) or the fact that SATA controllers are more complex than NVMe ones, because they have to do everything an NVMe controller does, but also they have to emulate a mechanical hard drive and map requests to sectors, cylinders, tracks etc and support/leverage queue management features like NCQ which are for mechanical disk heads primarily. Yes, the MX500 does all this so well that it's often indistinguishable from a decent modern NVMe drive, but all that extra complexity has a very real cost overhead.
The other issue of SATA is transfer rates. Right now there's no killer feature that requires the sequential speeds of NVMe drives. Video editing with large RAW footage is certainly one of those features, but it's not something your average joe will do. Average Joe is currently unfazed by transfer rates because most of what Joe does is small transfers where SATA's transfer rate disadvantage only results in a fraction of a second here and there.
