You're looking at the pool prices. That accounts only for 20-30% of the final bill people has to pay. The rest is taxes (and even taxes over taxes) and regulated costs, which by the way are quite opaque, despite they make some cosmetic effort of transparency.

The rationale, they say, is that the spanish grid is "solid" and we rarely have problems, which is true but I don't know to what extent this explains the prices, or if cheaper countries do really have much more problems than us, which I highly doubt.