In general your idea is good: why use a costly resource when a more affordable one does just as good? But the author (glumly) counters this: so many consumers

In general your idea is good: why use a costly resource when a more affordable one does just as good? But the author (glumly) counters this: so many consumers of truffle receive the substitute which isn't quite as good, and they think that's the true taste of truffles, but it isn't. So they walk away from the experience thinking they've experienced the taste of truffles, but they really haven't. If the truffle substitutes were exactly as good, then your point would hold, but in the case of truffles, at least according to the author, the substitutes don't have the same taste or aroma, or may be truffle but a less palatable species.