external benefit confusion
Not sure I understand your confusion.
Fruits provide external benefits worth $X$ to honeybees, honeybees provide external benefits worth $Y$ to fruits.
Knowing all this, farmers and beekeepers agreed that farmers should pay beekeepers amount $Z$, which probably comes close to making things even, meaning $X + Z = Y - Z$. Since $Z &gt; 0$, $X &lt; Y$.