...
Actually I think the shit scenario is less improbable.
Shit has been considered art in the past, and people are willing to pay a lot for art, so who knows?
...
Yeah, but my shit's value is derived not from its artistic merit, but simple scarcity--there is only so much shit I could produce in my lifetime.*
It's much like gold and Bitcoin, my poop is. The supply is limited, demand unlimited

profit!
*
I would have to strike a fine balance between eating as much as I can (thus maximizing daily poop output) & eating in moderation (thus extending the duration during which I could work on pooping).