Today’s New York Times carries an article about high-speed rail in California. It seems that if everything goes according to plan and there are no difficulties or delays, the state will spend $68 billion to build a 520-mile railroad to be completed by 2029 ($131 million per slowly built mile).
How do the innovative geniuses of California compare in performance to the plodding dullards of China? http://en.wikipedia.org/wiki/High-speed_rail_in_China says that the Chinese will spend $300 billion to complete 16,000 miles of track by 2020 ($19 million per quickly built mile).
[You might ask whether or not performance is comparable. Wikipedia says that the Chinese trains can go 160-220 mph. Wikipedia says that the California system will have speeds of "over 200 miles per hour" (and also that the system might cost closer to $91 billion.]
Update: Another way to look at this is what it would cost to fly people back and forth between these destinations efficiently. Absent government regulations to protect local carriers and unions, Americans would be flown around by an efficient airline such as Ryanair. This costs about 7 cents per seat mile (source). So the cost of taking one passenger on a 520-mile trip would be about $35. Suppose that the $91 billion estimate is more realistic and that, instead of being used to construct this railroad, it were invested in infrastructure projects in growing economies and yielded a 4 percent real annual return. That’s about $3.64 billion per year in cash, enough to fund 104 million one-way trips every year (i.e., 2.7 trips per year per current California resident). So instead of paying $91 billion for this railroad and then also paying for tickets to ride on it, Californians could use the money to pay for virtually unlimited free north/south air transportation (http://www.transtats.bts.gov/ shows that Americans and foreign visitors only got on airliners about 643 million times in 2013).