I pay 3,600 per year for my 2002 murcielago in Florida, because I dont have a USA drivers license yet, if not it will be a lot cheaper, is a full cover policy, but in case of a total lost the must they pay is 150,000 us for the car.
I believe you should get another insurance company in Spain, I have in Madrid a 1993 Ferrari 512tr and I pay around 2,400 euros per year, for almost a full coverage, it doesn't include broken windows, and fire.