Tolls Violate the Dormant Commerce Clause?

The Times reports:

Massachusetts and Rhode Island use electronic toll systems to charge their residents less than out-of-staters at some bridges and tunnels. Now two new lawsuits filed in federal courts say the practice is unconstitutional.

I would think that clearly violates the Dormant Commerce Clause. Massachusetts and Rhode Island are treating out-of-staters differently than in-staters, merely because of their out-of-state character. Thus, these laws are facially discriminatory and subject to virtually per se invalidity.