There are myriad other factors that go into this, especially just general inflation, which will likely fill the price gap by the time memory costs go down anyway.
I know I'm comparing apples to oranges here (new to used), but I started buying used 1L PCs instead (Lenovo thinkcentres) for about $20 the cost of a RPi 5 - but with the benefit of it actually coming with the cooling and storage it needs to run and is upgradable, plus runs Intel.
The amount of times I've had a Pi just self-destruct on me is ridiculous. They are known for melting SD cards, and just this week I had one blow the power regulator over USB power and still get hot enough in 2 minutes that it burnt me to touch it. They are considered cheap commodity computing and they aren't cheap enough for that any more.