ROAS is a channel-level efficiency metric, distinct from overall profitability — a campaign can have a high ROAS and still be unprofitable once product cost, fulfillment, and overhead are factored in, which is why many teams pair ROAS with a target based on actual margin (sometimes called break-even ROAS).
ROAS is heavily influenced by attribution model choice: last-click attribution tends to undercount upper-funnel channels like display and social, while data-driven or multi-touch attribution spreads credit more accurately across the full path to purchase.