When a brand tells me "we tried scaling and it broke", what usually broke was not the campaign. It was the assumption that the next rupee would perform like the average rupee.

Average versus marginal

Suppose you spend ₹10 lakh a month at a 3.0 ROAS and decide to push to ₹15 lakh. A month later, blended ROAS is 2.6. That looks like a modest dip.

It is not. The first ₹10 lakh still returned roughly ₹30 lakh. The total is now ₹39 lakh. So the additional ₹5 lakh returned ₹9 lakh: a marginal ROAS of 1.8. If your break-even is 2.0, that increment lost money, and the blended number hid it.

Every channel follows a diminishing-returns curve. The question is never "is this channel profitable?" It is "is the next unit of spend profitable?"

Finding your curve

You do not need a full media mix model to get a usable answer. You need disciplined steps and honest measurement.

  1. Increase spend in deliberate steps, for example 20% at a time, and hold each step long enough to exit the learning phase.
  2. Measure the increment, not the blend: additional revenue divided by additional spend, ideally on first-party order data rather than platform attribution.
  3. Plot it. Three or four points are enough to see where the curve flattens.
  4. Set a marginal guardrail. Scale while marginal ROAS stays above break-even plus a safety buffer. Stop, or shift to another channel, when it does not.

What the curve tells you

The shape of the curve is a diagnosis in itself.

  • A steep early drop usually means a narrow audience or a single tired creative. The fix is creative volume and new angles, not more budget.
  • A gradual slope means the channel has room. Scale with confidence.
  • A curve that drops off a cliff at a specific spend level often points to a structural limit: market size, a single SKU carrying the account, or frequency saturation.

The operating rule

I give teams one rule to keep: we scale on marginal returns and report on blended ones. Leadership needs the blended view for planning. The people moving budgets need the marginal one, every week.

It is a small change in reporting. It is a large change in how much money you keep.

Shiva Sharma is a global growth marketing leader and the author of The Movement and Nobody Is Thinking About You. More about Shiva

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