Wow, thats worse than I thought. Due to finite lifespan of the SSDs, I think alot of the profits goes into funding new SSDs....I started chia farming because of TomsHardware and while a fun project it is not profitable. I have a Pi 4 8GB running 9 drives that equal 47 TBs 416 plots in Space pool.
The hardware cost about $1300. More if I count the extra ram, which I look at as an upgrade that helped the systems as a whole.
With madmax plotter and 2 WD 550 NVME 1 TB on a 2700x I could plot 31 plots a day (2 weeks to plot the 416). And the plotting used 20% of each of the drives life span.
The farm running on the PI 4 wins about $1.5 everyday at current prices so it will only take over 5 years for ROI. On the pool right now you can get 0.00235 chia per 10TB every 24 hours.
And the best price on HD are at Best Buy $104 for 5TB easystore. If you use the easystore they are 2.5 laptop drives that do not need additional external power other than the USB hubs. Less power cords, smaller size, lower power usage. Not sure about life span. I would assume the full size WD like the 8 TB at Best Buy for $180 would last longer since they use the WD Red 7200 drives. But the cost per GB and the power is higher.
Because of the current price of chia ($190.94) it is not a good ideal to expand the farm by adding more space. If it goes back up to the high of $1600 I will add more HD.
Note: The Pi farm just sits behind my monitor using very little power and making no sounds and no additional work. And all hardware can be reused if I ever stop farming.