About 10 years ago I was in the market for a used Toyota Camry, so I wrote a script that scraped the used car classified and extracted models within a 4 year range and within price & mileage caps. This got plotted out into 4 overlaid point series, producing graphs that roughly looked like 1/x, roughly 2-300 datapoints total.

With that in hand I went to dealer offering the best match, told them which car I wanted and how much I was going to pay for it. Put the graph in front of the salesperson who was floored, went back to his manager, and gave me the car for that price.

That was before I even knew what the term "market price" meant.