"If you already pay for shipping then shipping adds no marginal cost."
well, yeah. That's what the phrase "marginal cost" means: if it costs $x to do something N times, and $x + $y to do something N+1 times, $y is the marginal cost.
alt Hacker News
well, yeah. That's what the phrase "marginal cost" means: if it costs $x to do something N times, and $x + $y to do something N+1 times, $y is the marginal cost.