@166266, you might want to consider putting your post OUTSIDE of the quotes.
$3500 doesn't take into account that, when you order it with the car, they REMOVE the 19" wheels, so that could be considered the $1500 price difference between what has been said. Though, if you follow the straight pricing on the shop, the 20" is "only" $1k more than the 19" (though I didn't fully calculate price difference of tires).
While it's probably true there will be plenty of people who want to swap from their 20" to 19" inch, I'm not sure they'd want a straight swap without a bit of cash on top of the 19". As I just mentioned, there's a price difference between the two wheels. So, $2k might be a bit much, maybe $500 to $1k in additional cash wouldn't be unreasonable.
For the person with the 19", they would've paid $2k to get the 20" with the car. Or they'd have to pay $3500 for the 20" winter package from the shop, maybe have the tires swapped and finally sell what they don't want (or keep it all as is). $500-$1k means they pay a bit, but not the full price.
For the person with the 20", asking for $500-$1k means they lost a bit compared to the $2k they spent for the option, there was a reason they chose that option, so assuming they got that reason fulfilled, it should be counted as a positive still. Asking for no money, on the other hand, seems unreasonable no matter if they got whatever else it was. $500-$1k means they get some money, without completely taking advantage of the other side and getting whatever the reason to selecting the 20" in the first place.
So yeah, $500-$1k could be considered a compromise between the two.