Ask HN: Have you ever buy a product before it was built?

Did you (or your company) ever committed to pre-buying a new product or service, before it was even built?

What were the conditions of payment, and how confident were you in your purchase?

I often hear that, for B2B products and services, you can (and maybe should) validate your idea by getting pre-sales. For B2C, I guess there's Kickstarter, where you might get "fans-only" benefits for being an early-adopter.

In B2B, I'm wondering what it's like to be on the buyer's side, and why a company would choose to pay for something that doesn't even exist yet.