To be fair I think once artists get to a certain level of production in their stage shows they probably don't have a lot of input into how much tickets should cost. Of course the point remains they if he wanted his shows to be accessible to the most people he could cut down costs considerably but that kind of goes agains the spirit of shows like "The Wall" which have a level spectacle associated with them.
I don't believe that for a second. When you have as much clout and star power as Roger Waters does, of course you have a say in ticket costs, unless you pass it off to your management and then steer clear of that aspect of the business so you can claim plausible deniability.
I think artists cede a ton of power to the production companies nowadays. My hunch is that LN probably offered him X millions of dollars up front for a tour, win or lose, and they take care of the rest. Moreover, if he says that he wants normal fans to be able to enjoy it they're truthfully able to say "hey, we've got seats for $35 ea." Of course there aren't many of them, they truly suck, and TM's TT&L nearly doubles the cost, but from their perspective it's still accessible to all.
edit: Also, I have to point out that he sells >95% of his exorbitantly priced tickets, so a great deal of this is market demand. An argument that the scalpers have been making for years is that concert tickets are undervalued. In their case I think it's a rationalization, but in Roger's case he does seem to be hitting pretty close to the mark in terms of value.