Here are calculators to help you determine what KPI goal is right for their business: https://docs.google.com/spreadsheets/d/1xbl5r5fYG_6_laNY8S24vT6IyOYoRnfZpyKG0itOMew/edit#gid=463182576
Notice how the numbers used in the calculations are variable numbers (any number that will scale as the sales scale) and any steady numbers (like monthly fees, overhead, most of the business’ labor costs, etc.) are not included.
What is a good return on ad spend? - I used to stress about every eCommerce store that has less than 400% ROAS, but lately I am realizing...repeat business is a huge factor. A business like VitaminsOnly.com.au might sell a $15 product, but that person has a good chance of coming back for a refill or cross-selling to other products. Whereas something like a no-touch Covid Vita Keychain (vitacreations.com) is really a one-time purchase situation.
Account-level goals vs. campaign-level goals - Keep in mind that you can talk about the KPI for the entire account and each campaign can have it’s own KPI. For example, a business might set a ROAS goal of 400% for the overall ad account, but their “video shopping campaign” might only need to get a 200% ROAS in order to perform profitably, because video has the added value of brand awareness and feeding the “smart shopping campaign” with a pre-warmed-up audience to unofficially “remarket” to.