Well, HD provides plenty of room, but like you said, high on the cost and low on the performance (unless you're planning on doing 80mph everywhere). I own a Yamaha V-star 950 which is an awesome bike, but for someone tall, the seat is at a short 26.5". You can look into the Yamaha Raider, Warrior or Stratoliner models which would probably afford you the space and seat height that you require. I'd also research a bit more comfortable bikes like the Kawasaki Vulcan or the Honda Goldwing. They are the luxury metric cruisers. For the 'Wing, the price maybe high, but so is the performance and enjoyment while keeping maintenance costs low (father-in-law owns a 1998 'Wing). Suzuki makes a nice Boulevard model which I've seen with nice, roomy seats and they also have the M and C class cruisers.
But...there's always a "but"...I'd suggest looking at a dealership first, getting an idea of what models fit you best, then research their specs and performance and then see what personal experiences are here on the forums for each specific model. It took me over a month to choose and settle on my bike. That entailed visiting the dealership 3 times a week, reading all the reviews and spec sheets for my bike (that were available) and sitting on other bikes just to make sure that what I had chosen was truly the best fit.