The issue is that Spain has three interconnected neighbours (France, Portugal and Morocco) and all of them are overflowing with electricity.
The best candidate for lowering prices would be France, but France would most likely re-export that electricity to other countries, and paying to build up the internal grid to carry electricity that is neither bought by nor sold to French actors isn't very attractive.
Ideally Spain would interconnect with Italy, but that's more expensive.
Hvdc in the ocean requires way less right of way than hvdc over land. Running oceanic hvdc from Spain to Germany might have some trouble in the English channel where it would be in territorial waters.
The best candidate for lowering prices would be France, but France would most likely re-export that electricity to other countries, and paying to build up the internal grid to carry electricity that is neither bought by nor sold to French actors isn't very attractive.
Ideally Spain would interconnect with Italy, but that's more expensive.