Idea validation through email?

I've always found the "I would pay..." validation to lead to false positives because often times people have a hard time being realistic when they hypothesize what they would pay for something. Nothing is more validating than having someone choose a pricing option thinking their credit card will actually be charged (or better yet charging them for it) . There are ways to test this before you really dive deep into building something.

For one, you could set up a landing page with the different price points and have different features for each tier. Have a "Sign Up" button as if you're already selling whatever product you're launching. When someone clicks on it, tell them--that the product is in beta and they can sign up on a waiting list for the release and you'll give them early access at a discount or whatever.

Then using the Tag Manager in Google Analytics, set up an events tracker to figure out which tier more people are clicking on to start getting a better sense for the price point you should be targeting.

Also, an important note here--if your product is something that needs to be demonstrated to build trust, a simple landing page test like this is not going to build enough trust quickly enough to get accurate data. People may say "no thank you" before really considering your product as a viable option because they don't see how the product would help them.

Hope this helps!