I don't know about that price thing... I agree, SOME general idea is a big help to the buyer.
But I own a small business (wallpaper installation), and I NEVER quote prices over the phone. Well, sometimes a very vague price, with a stipulation that it is not a definate price, until I see it and do a proper bid.
As soon as you quote something without seeing it, even a "ballpark" figure, the client thinks that's the set price, and then you get there, and it's not what he described at all... all sorts of extra work you weren't aware of, special situations, etc. Also, if you give a price per sq. foot, they go and figure it up themselves, and think they know what your price should be, but, of course, they have no clue about measuring, and they forget other things that should be figured in, and then they get ticked off at you, or think you're cheating them, and they think they know more than you.
I don't know the answer to this... Probably need more suggestions from people.