"As low as," in other words, "at a minumum."
And you need one roundtrip ticket per person. How many people are driving from Tampa to Orlando and back with only one person in the car? How much are train tickets for your wife and three kids on your way to the Magic Kingdom? How does that compare to the price of gas even at $5 per gallon?
With the HSR, everybody has to continue to "pay" for the unused seats...