In short
- The right number comes out of your margin, not out of a benchmark.
- Spending more on a product that cannot carry it makes the problem arrive sooner.
- Budget is a decision about which products to back, not a single figure for the account.
Where does the number come from?
Start with what is left after Amazon takes its share and the product is delivered. That is what advertising has to come out of.
Every product has a number. The account does not.
What if the number is uncomfortable?
Then the answer is usually the price or the product mix, not the campaign.

