I have the 15inch steel wheels, see pix below
found these for sale
^^- these are the same price as getting new tires alone and have a little over 50% tread left
I called the dealer they don't know but weighed a Scion TC alloy for me they had, it was 20lbs not lots of help but thanks, Yaris should be less. Of course factory alloys will be heavier than aftermarket, but they are tough and should be well made.
looking on eBay now