The speed and price difference between what Apple offers and what third parties (who are the OEM's anyway, Samsung, Crucial/Micron, WD/Toshiba/SD, are Apple's suppliers after all) offer is a fact, not an opinion. The 500GB SSD in my 2018 Mac Mini is way slower than the WD Black 500GB NVMe SSD in my desktop PC. The Mini caps out at 1800MB/s read, 1000MB/s write, the desktop over 3000MB/s read and 2300MB/s write. No question which is faster. The WB black was $139 Cdn for 500GB, the Mini upgrade from a 256GB drive to a 500GB drive was $240 Cdn. If that's not Apple gouging, I don't know what is. Now it could be the Apple is opting for slower MLC based drives for better longevity, but my guess is they are just massively over pricing the upgrades to increase profits. So as I said, it's all about the money. I like Apple products, but I will not be an apologist for them.
Wouldn't hang onto a machine with a Core 2 Duo, although my sister has that 2007 iMac, they hardly use a desktop computer so they don't care. I don't keep a machine for than 5-8 years. Do I upgrade them? Of course, I'm not going to buy a new machine just because I need more storage or RAM, that's just stupid and waste of money. Of course I do it myself, not have some hack making $10 an hour in a back of a mom and pop computer shop that chargers $100 an hour do it. I have a custom PC (2018 parts), 2018 Mac Mini, and a 2012 Mac Mini (media centre use only). Never had a hardware failure on any Mac I've bought, other than a Gigabit Ethernet G4 that had a power supply die. Stuck it into a G4 I picked up for $20, swapped parts over (the old one was better), and still boot it up for some legacy OS9 stuff once every few years, and that has nothing on our 1980's Mac. Old stuff is old, but I don't mind my little museum pieces.