New York to Porto, Portugal $471 RT on Iberia

Iberia is offering a Round Trip Flight: New York to Porto, Portugal (1-Stop in Madrid) starting from $470.90/person (price includes taxes and fees).
Departs (JFK): May 11-24; May 28.
Returns (JFK): May 18-28, 30-31; June 1-2, 5?
http://www.iberia.com/us/