Spanish return is for every 60 cent it spends and given Spanish VAT is 8% then even if tourist only spends €10 on a meal the state is ahead.
Spanish VAT is 18% so that tourist would only have to spend €3.35 to recover the amount paid to the airline.
Thats what a drink in a bar (Not even mentioning the alcohol duty). Spain would even earn money on someone buying a McDs. Money well spent I think.