Two write-ups from real campaigns. Both name the budget, both show the working, and both say what the numbers cannot tell you — which is the part most case studies leave out.
47 leads from $179 of Meta ad spend on a lead-form campaign for home tours — roughly 4× below the published real-estate median. The full arithmetic, including what the conversion rate did.
$11,113 in sales at a 4.08% conversion rate for a small Shopify store, with two thirds of revenue traced to an Instagram audience built without ad spend.
Both name the actual budget, not a range. Both show the arithmetic, so you can check it. Both are campaigns run end to end rather than a slice credited after the fact — and both say plainly what the numbers cannot tell you: the real-estate one was a small spend over a short window, and the Instagram one took two years of posting nobody paid for.
What you will not find is a logo wall, an unattributed percentage, or a result with the spend removed. If a number here matters to your decision, the write-up shows where it came from.
Both predate Kerr & Company. They are here because the method is the one still used, not because the brands are impressive.
Tell me the business and what a new customer is worth. I'll tell you what I'd try first, what it would cost, and what the numbers would and would not be able to tell you.