All of these recommendations were WELL under $100 when we visited tho we were there off season in November. They were all relatively small which we like.
Cordoba--Hotel Mezquita, quirky, clean, HUGE room, great, helpful staff, 15 feet from the Mezquita.
Sevilla-El Roy Moro, tons of local charm, very helpful staff, center patio with rooms surrounding, great included breakfast, about 5 minutes from the cathedral and Alcazar
Granada--Hotel Anacapri, spotless, great included breakfasts, great location near chapel and cathedral
Madrid--Hotel Europa, steps from puerta del sol, super clean, fresh and new, helpful staff
and should you decide on an overnight in Toledo (where hotels are much less expensive than Madrid, Hotel Santa Isabel, nice location in quiet part of old town, great views from roof, included simple breakfast.
I booked all these hotel directly via email indicating I found them thru the RS guide. It got me a little perk at each one. At this point I can't remember which ones gave me what. Typically, a room with a view and a better rate. A couple it was the included breakfast (Anacapri, for sure),