"Speed costs, how fast can you afford to go?" Doesn't matter if it's cars, motorcycles, trains or sailboats. It's not a linear increase either.
Having said that, what I'd love to see is all fixed rail infrastructure turned over to a non-profit corporation. Private or public rail companies with the rolling stock would pay fees to run trains on given schedules controlled by the infrastructure company, with priority given to passenger trains. The fees would be enough to cover the costs of rail maintenance and expansion.
With railways open to anyone with rolling stock, competition is increased. Exclusive routes would be eliminated, which would help reduce freight rates.
Over time, separate passenger rail lines would be developed, at least partially subsidized by fees on the freight companies, as passenger rail typically has very thin margins.