Chia is just "proof of prior work" and as such has the same arms race problem as bitcoin. People aren't just buying a few TB, farming it and being content. They're building farming rigs and piling on the storage constantly. It just consumes power AND storage.
I currently have 4TB of free space. I could plot them which would result in an estimated $7.57/month of income per month.
But.... that's not a constant $7.57 each month. Instead, it's a 1.5% chance of winning a single payout of 2 XCH each month. I could reasonably expect to go five years, never winning a single XCH.
Who knows what the value of XCH will be then. There has been a pretty solid downward trend in price since May, contrary to most coins, which started trending up again.
That changes the calculation significantly.