Can government make $500 m a year? Sorry I doubt it. The socialists will never allow the toll rate increase quietly and the government will never have enough courage to offend anyone to pass increase the way the privately held 407 does.
(Lucky me I had only gone on 6 or 7 times and not even once that last 10 - 15 years. I just refuse to pay.)
BTW if the 407 does make $500 m a year the way you claim they do the provincial share of corporate tax, both in HST and income tax, is more than $100 m a year. Do you remember any crown corporations produce that much tax revenue for the government?