I think it's more reasonable to compare the progression of 3D printers with the old 2D printers. Back in the day of dot-matrix printers, consumer level machines were slow, noisy and of low quality. Industrial machines were fast, really really noisy and of low quality. We've seen massive increases in quality, massive reductions in price but not a comparative improvement in speed. I'd venture a guess that 3D printers will go the same route - price will go down by a long way, quality will go way up but speed won't improve at the same rate.