Way back when I got my PPL, the regulations just said it was legal to "share expenses" with no definition of how much of a "share" the passenger paid. It was technically legal for me to pay $1, and the passenger to pay the rest.
My dad was an insurance claims adjuster. In our state there are a lot of small towns separated by hundreds of miles. I would take my dad on rounds by plane where we would visit several cities in one day, and be back by the early afternoon. The insurance companies paid him a mileage rate based on the road distance between these towns. Usually that would pay for almost all of the plane rental (which included the fuel). I basically got to fly for free.
A few years ago, the regulations got "clarified" by the FAA with the whole ratio calculation thing. Now the sharing of expenses needs to be calculated correctly. Back 20 years ago, this whole Flytenow thing might have worked. Not now for sure.