Housing prices are probably not as low as you think either. Of course, it all depends on which area of the island you're looking at. Construction of luxury condominiums have been rampant over the past few years, and many of these condos start at around $325K. The price of electricity is a whole other issue. To sum things up, it's a foolish idea to think of Puerto Rico as a cheap place to live. Perhaps, if you're coming from either Western Europe or New York City, you'll probably think the island is a steal. Otherwise, do not be surprised at Puerto Rico's high cost of living. The only two things which I found to be cheaper on the island are movie tickets (an average of $6.50) and gas prices (as of today, an average of $0.45/liter).
(Image obtained from www.economist.com)