Telepizza is the Spanish equivalent of Pizza Hut or Domino Pizzas, with around 600 restaurants across Spain.  So wherever you are in Spain, you're likely to be near a Telepizza restaurant.  Their pizzas are pretty good but they're not the cheapest, but thankfully they regulalry run special offers.  You can find their current special offers on their website here:

http://www.telepizza.es/productos/promociones

The pick of the deals at the moment are 3 family sized pizzas for€30 (1o euros per pizza).