Outside of arguing about Apple's SSD pricing – which isn't going to change unless there is a drastic drop in SSD chip prices, and even then – what is a good, reliable, outboard, NVMe capable SSD enclosure that works with USB 3 or Thunderbolt 3 and preserves the 3.3Gb read speeds? It is the cost of such an enclosure PLUS a NVMe SSD card that folks will have to shell out to expand the Mini's base storage. Any such enclosure that doesn't provide near native speeds doesn't count.
Hell, I'd like such an enclosure to expand my USB-C MBP's storage, forget about the mini.
This: https://www.tomshardware.com/reviews/netstor-na611tb3-thunderbolt-3-nvme-portable-ssd,5359.html which is $360 for just the enclosure. On the plus side it has two (2) M.2 sockets... and it comes with a Thunderbolt 3 cable, although a very short one.
Here it is @ Beards & Hats: https://www.bhphotovideo.com/c/product/1381233-REG/dynapower_usa_netstor_na611tb3_thunderbolt_3.html