Well, 'pay more based on a true story' might imply that there is a reason related to a factual account that leads to an increased payment. Maybe it's a donation situation where you pay more to a cause because you've heard a true story about its importance and the real impact it has. It could also be in business, where a company charges more for a product with a backstory that is based on truth, such as a handicraft made by a particular community with a real, inspiring story behind it.
Well, actually, 'The Devil to Pay' is purely fictional. The story and characters were made up by the author's imagination and not drawn from any real-life incidents or people.