That is shockingly cheap for NVMe.
Oh, I also threw in a pair of nvme drives for caching. It noticeably speeds up read speeds. You can use non-synology drives but it'll limit you to using for caching as opposed to storage but that should be fine seeing as you will have 4 bays for storage anyways.
These are reliable and very cheap at the moment. You'll need a pair of them.
https://www.amazon.com/gp/product/B08X4Z4R1Y/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Discussion
Yep nvme prices have come down significantly! These Intel drives have been rock solid for me so far. Cheapest I could find anywhere. And they're $10 cheaper now than when I got them last year.
Now I just need a cheap 2230 for my surface pro. 😉
Oh good luck lol. I haven't come across any particularly cheap 2230s as of yet. 1tb for $88 seems to be the best so far. At least it's gen4 if your surface supports it...