Leif
Adventurer
Based on that beautiful graphic depiction of Neuschwanstein, I have to say that any similar treatment for the abandoned keep that the wizards are hopefully going to establish as their base would cost considerably more than 12-15,000 gp, based mostly upon the interior pix of the castle. Serviceable and secure you can do for 12-15,000 gp. Opulent, positively decadent, slap-yo-momma rich will be more on the order of 30-35,000 gp. And, of course, that's only the construction cost, not upkeep, maintenance, cleaning, repainting, repairs, etc., to say nothing of the cost to feed the crew required to run the place.