The bridges crossing up the Seaway valley are pretty cheap with starting with the most expensive
Rates posted are for single trip with car and light truck:
St Lawrence International Bridge Crossing(Three Nations Crossing) $3.25 Can/US ON-138/ NY-37
Ogdensburg Bridge and Port Authority $2.75 Can/US ON-16/NY-812
Thousand Islands Bridge Authority $2.50 Can/US ON-137/I-81
The Three Nations Crossing rates may go up with the Proposed North Channel Bridge reconstruction.
Other bridge/Border Crossings:
Ambassador Bridge Authority $4.75 Can $4.00 US ON-3/I-75/96
Peace Bridge Authority $3.00 Can/US E-Pass $2.70 Can/US ON-QEW/ I-190
Blue Water Bridge Authority $3.00 Can/US ON-402/I-69/94
Matty Moroun's bridge is the most expensive for Canadians, and that I don't think will change even if he gets to build his new toy, um I mean bridge.