Going on our own
This option could be cheaper but also has more risk.
Same dates of travelling but for 2008 prices are arround $1000 round trip, and each hotel night could be arround $40 each person.
Transportation in train is cheap. Madrid-Palencia round trip is arround 19 Euros. With high speed train is a little more expensive. Trains are very frequent
Having our "base" in Palencia, we can travel to Cantabria to spend one day in the beach, or to historic Burgos and Leon, to the medieval towns of Avila and Salamanca (oldest university in Spain and one of the oldest in Europe), to Madrid, to see castles in Segovia, to see roman archeological excavations, to a car factory, to agicultural centers...