An important factor in pricing car hire, especially long-term, is the high tax rate in Spain (16%!) of the total rental. For long term hire, a lease may be more cost-effective because the rate structure changes for leases; rental of more than 23 days is almost always more money than a lease. And, picking up a leased car across the border in Perpignon, France, (not that far from Barcelona) will save lots of money because of lower taxes! There are also location surcharges in Spain, which vary by city & airport, & optional insurance & waivers (loss damage waiver, personal accident & theft protection); in Spain, these can add well over $700 US to the cost of a monthly rental.

I was not sure of the length of your rental, so some of this info may be not quite on target!

My best advice is to read the rules of the rental carefully at the time you make the reservation, as the total cost of the car is not always the quoted rental rate. I've seen too many travelers, stumbling off an international flight with the thousand-yard stare, trying to cope with a car rental counter agent in another language, & trying to figure out what all the circle here, initial there stuff is all about! Once you've returned home & the bill comes thru on your credit card statement, it's very gnarly to get erroneous charges reversed.

Gail In Eugene