Why is a 19" car tire way more expensive than a 16" tire? If you compare a 225/45/19 with a 215/65/16 they are double the price even though they have the exact same outer diameter.
One possible answer is the smaller sidewalls need to be more stiff but a 225/55/17 is still more expensive than a 215/65/16. It would need marginally stiffer sidewalls and will almost require equal amount of material.
I was also wondering what advantage will a 19" tire offer as compared to a 16" tire? Given that they have an almost identical outer diameter they should wear out at the exact same rate. The only thing that comes to mind are better looks.