Take a "sample" of pumpkins, weigh them, have the humans write down their prices and fit a pumpkin weight -> price model. A pumpkin is sort of a hollow shell if

Take a "sample" of pumpkins, weigh them, have the humans write down their prices and fit a pumpkin weight -> price model. A pumpkin is sort of a hollow shell if you discount the weight of the goop inside, so the weight should increase with the square of the diameter.