Have you ever pre-sold* B2B SaaS?

Have you ever pre-sold a B2B SaaS before? Or do you know any examples of it?

• By pre-sold I mean before you even built a landing page or bought a domain name.

My main concerns with pre-selling are:

1. Wasting money on ads to test demand, it is relatively expensive these days, running into the $100's for a reasonable sample size.

2. Wasting effort doing a lot of prospecting when I don't have anything to demo, so losing them in the month or 2 it will take to build something out.

Maybe these are excuses?

Please comment below with your experiences, I'd love to know what you pre-sold? how it went? or other ways you tested demand (in B2B)?