Hark! Is that a tree falling in the distant forest? Or the wail of a retired lumberjack?
Can't reverse my thinking that way, because I don't know where I'm going exactly and I'm willing to walk some of the way. Actually, my walking target is still 10,000 paces per day, so I don't even want to get too close to my various destinations.
Your price-inversion idea seemed more promising, but I haven't been able to make it work so far. I do have a solid example (of a free bus) to work from, but it fell flat on many Japanese searches. There are several webpages with various lists of buses. I focused my search on the station that is the terminus for the free bus I know about, but that particular bus doesn't appear on any of the lists... I was hoping to find it there and see how the free status was indicated, but most of the lists don't seem to have any fare information. The example bus is a regular municipal bus, but apparently it's regarded as some kind of special charter route and therefore doesn't really count.