[Jonesy55]

The savings on employer healthcare costs would seem to be a big plus for Toronto. Does Canada have higher rates of employer payroll tax type costs equivalent to Fica to reduce that advantage though?

As has been said, I very much doubt Amazon would look at just costs/incentives, the ability to get the best human capital will no doubt be #1 priority but the costs /incentives might well make the difference between a few cities that all score well on the first point.