I was travelling to LAS with 5 friends and we all bought our tickets individually because 6 at once was pricing higher. It turned out that 5 tix were left at the cheap fare and only 1 tickey was $30 more. We ended up splitting the extra cost among all of us.
I agree that it would be helpful in sitiuations like this if the price per ticket was broken out i.e. for three tickets one at $89 and two at $189. Airlines can problably get away with just pricing all tickets on an itin at the highest price and people won't notice.