“In my case I knew I needed to make about $20,000 to fund let's say 3 months of my life in order to work on this thing. So I worked out how many people I would need based on my target price point.”

Set a concrete runway target — work backwards from $20K to customers, list size, audience

Validation has a concrete dollar number tied to how many months of life the founder needs to fund. Working backward from runway to customer count to email list size turns vibes into a math problem. The pre-sale either clears that bar or the idea isn't worth quitting for.