After making the flight home, I can now intelligently answer my own question!
The allowance for the amount of merchandise that can be brought back tax free into the US has been recently raised to $800 per person. Even though the the stewardess stated it was $400, said it was the wrong amount but "it was on the card"!
Anyway, I hope this info will help travelers in the future.
By the way, Hotel Plaza Mayor was great. Also went to Grenada, Cordoba, Ronda, Sevilla, Zafra, Santiago, a night in Leon and to the cities around Madrid. My only mistake was in not going to Zamora. Next time...