"Falcon is right
"That is an excellent airfare, but you have additional travel expenses, and time, to get to starting and finishing points. I have found that an outbound flight to my starting point, say Pamplona, and a return from Santiago de Compostela, is less expensive than going to Madrid, then taking local travel. Priceline is not useful for these open-jaw bookings. My experience is that you have to go directly to the airline website to book them. American, British Airways, and Iberia code-share, so they often have the best connections."
I booked MIAMI-LISBON and return SANTIAGO-MIAMI for 867.00 in American Airline. (You always buy your tickets -at list from USA- on a Tuesday after noon, 6-8 weeks before departure. it is cheaper). I will start from Porto but I want to visit Fatima before start el camino portugues