What's the cheapest way to travel from Toronto to Niagara Falls and back?

Coach Canada is charging $30 for a two way trip, I think that's a little much.
Do you know another bus company or some other way?
I'm only 18 so I can't rent a car....
Could I take a casino bus? I hear they cost less, but am I old enough?
I'm going with like 9 other people.. but I think we can travel separately.
Any suggestions would be appreciated.

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