I find that there's a very big difference between people saying that they'd be willing to pay something and getting these people to actually pay for that thing.

The rate of false-positives in people indicating they'd buy something before being pressed to buy it is very high. This is speaking from first-hand experience. Sometimes having 0 customers and seeing whether people will actually buy it is worth more than asking people if they'll buy something without putting it to a real test. In fact, you might come to different conclusions about what is important and not if you go based on what people say they will pay for vs. what they actually pay for.