Okay, let’s tackle this. So David Lipp has an impressive 51 years of experience as an architect, which is extremely rare. His position as President Emeritus at a prominent architecture firm like Helbing Lipp Recny Architects adds to his credibility. His expertise in sustainable design and mixed-use projects is also in high demand. Considering his extensive experience, prestigious position, and specialized skills, I would estimate his hourly rate to be around $250. This is slightly lower than what I would expect for a top-tier architect with similar experience, but it's still a very competitive rate given his unique combination of experience and expertise.