These are high-end military carriers and vests. We purchase directly from a top military supplier (a regular at SHOT SHOW in Las Vegas), and then price them to you at 30% to 60% of anywhere else. For many reasons, quality and toughness is important- especially when dealing with an impenetrable best plate carrier.
A plate carrier also serves as a load-bearing vest. For training purposes, some athletes prefer to use a plate carrier, so they can easily add weight for a more strenuous workout.