My wife and daughter both have 8 GB Macs. The bottleneck is definitely not the RAM. It's their CPUs, old Intel models.
Even their 256 GB SSDs are fine. Actually both Macs shipped with 128 GB, but I ended up upgrading them to 256 within the first year, with inexpensive used OEM Apple/Samsung drives. For my wife it was her iMessage taking up 40 GB and some system files that put her over 100 GB total, greatly slowing that machine down. However, even today, she only uses 120 GB. My daughter only uses about 60 GB though, since most of her school assignments are done in the cloud.
I gave my 2017 27" iMac to my son. It's well-spec'd with 1 TB SSD and 24 GB RAM, but it's way, way overkill for him. He has similar computing needs as my daughter, so his 1 TB SSD has about 950 GB free.
Used. Not really a good price comparison.