Miner hardware price fluctuation

This is a very specific question regarding mining hardware that I hope someone in this subreddit can help shed light on.

I currently own 20 Antminer S19 miners that I purchased in 2021 for around 10K per machine. At the time I bought these machines, hash rate was relatively low so it was an excellent time to mine. Also at this point, the more dated Antminer L7s that had been around for 4-5 years were selling at a higher price than when they were originally produced.

However, as I look at the current price of the same machines I purchased, they have PLUMMETED down to 1-2K per machine.

The price of the hardware is obviously dependent on peoples’ willingness to buy it, and I concluded that this is made up of multiple factors, including hash rate, technological advancements in new machines, and Bitmains production costs of manufacturing the machines….. but I could be wrong.

Does anyone know what factors cause the price fluctuation in bitcoin mining hardware? Should I expect the market price of the S19s to increase in the future?