Parr never asks people whether they would use the product, and he never asks whether they would pay. He points to Rob Fitzpatrick's book The Mom Test for how to ask good questions, and he spends the first half of every call on one thing:
If they have it, he asks how they have tried to solve it, what worked, and why they are not already using something that exists. Those answers become the spec. In the example he gave, people said they had wanted a product like his, but the brands selling one seemed old school. Hearing that on call after call told him what his version had to look like.
The second half is the sale. He asks how much the product would help, then pushes for a number: revenue earned or time saved. Then he makes the offer. It will cost more later, it costs less now because they are early (his example was $500), and he will refund the money if they lose interest. Then he sends a link.
First half
Discovery
Broad, open questions about the problem. Have they tried to solve it, what failed, why they have not bought what exists. No pitch and no hypotheticals.
Second half
The close
Ask what solving it is worth, in money or time. Name the later price, the early price and the refund. Then send the payment link.