>>280689169
>since they have a lot of money from mass murder sprees, they can order the best food there is
You're reading to much into it; Ryo absolutely moggs most adventurers at monster-killing, so much so that his takings have to be planned around so as not to crash the entire magic stone market. It's been established this very episode that adventuring is the kind of job an orphan with zero-prospects, like Amon, would take up. Able and his party make bank because they're rare talents, and the highest-ranked adventures around- so much so that they're local legends. Yet even then, they have nowhere near Ryo's earning potential.
tl;dr: Most adventurers aren't rolling in money.