Wait. I say "how does wasting 10% have more impact if you waste 10% of 10 or 10% of 1000?", and they answer "it's just not worth doing it for 1".

I just don't see how this is related to waste. Of course if it's not profitable when you sell 100% of what you produce, then it is not profitable (that's a tautology). My question is: why is it more profitable to sell the same amount but to waste more?

Turns out someone explained in another comment [1], and the "it's just not worth it for one mushroom" just does not explain it.

[1]: https://news.ycombinator.com/item?id=48962668