Ticketmaster isn't the only seller. There is Ticketek too. And both have their own reseller market now. So even with them its hard to tell if the price you are paying is fair or not. (usually NOT)
Yes, their commission is high and people sometimes also put up ridiculous prices, not arguing with that. But I assume that if you really want to rebuy tickets, then if you buy ticketmaster tickets off the ticketmaster resale site and ticketek tickets off their resale site you should be "safe" from getting fake tickets or tickets that have been resold multiple times. And I think the ticketmaster resale site shows the face values of the tickets so you can see how "fair" the price is and decide if you want to pay it.