The only reason for this huge speedbump is that chip makers have been dragging their feet for the last 10 years with "just enough" memory.
Stuff is crazy expensive.
I also bought 96GB some while ago but after the initial increases, thinking I'll wait it out. Now 128GB is far more expensive than it was when I first looked. Luck has it I want DDR5 RDIMM as well, which seems the hardest hit when it comes to RAM prices, fun stuff.
The base price of a mini has only gone up $200 from $699 in 2020 to $899 today, and for $699 you only got 8GB of RAM instead of 16. Yeah the price has gone up but not nearly as much as you seem to be remembering...