In expensive Canada, about $0.07 / GB.
What does your ISP or Phone company charge YOU / GB?
In Canada, folks are charged as much as $10 per gigabyte. (Companies try to convince that there is a shortage of electrons traveling over wires or fibre. That’s a lie.)
Once the wires are in place, the cost for extra electrons is almost zero.
related – CNet – Are you overpaying for smartphone data?