You want to make a room 'perfect' for mixing and mastering? Are you planning a complete build from subfloor, ceiling, walls, and ventilation, as well as acoustic treatment? Then Mr. Brandt will be charging much more than $500. He is well respected, and I was about to pull the trigger on his design of my drum room. I had some unexpected financial problems, and had to bow out. He was still helpful in making it happen anyway. I would willingly pay him what he asks for his advice, if you are serious about getting the most out of your room. IMO, and from everything I have heard from those who he has designed and built for, he is worth every penny.