This is exactly how it works rates are adjusted to traffic if it is busy they go up. If usage falls they go down. It is priced to keep it from being to busy therefore not worth paying for. If it was cheap it would be clogged like the 401 they are selling a premium service.Here is my take on 407 pricing. It is based on observation only.
There is an optimum amount of cars that they would like to see using the 407. If you have too many cars, maintenance costs and wear and tear on the road go up. Also the road starts to slow down.
At this point, they raise prices to bring the number of cars back to optimum levels.
Sent from the future