Basque country is one of the richest regions in Spain, which is already a highly developed country. Not sure what you are talking about.
Basque country is, again, rich because it has an special tax treatment and could be considered a tax heaven to some extent.
I'd say its a well developed region comparable to Northern Italy. Both were badly hit by the Euro. Had they kept their own currencies, they'd be closer to Sweden or Southern Germany.
Spaniards tends to have this idea that Spain is a shithole when it’s really one of the best countries in the world.