As an addendum to what Indiction said

A lot of the more complex 3D models you see in games use various tricks to give the illusion of depth where there is none, and in this way they can make relatively simple shapes looks more complex than they really are. This is especially true when a surface produces no sillhouette - ie the player will never see the detail at such an angle where they can *see* the object is flat, but textured to look 3 dimensional

However that design has a lot of detail that can't be 'faked' - the deep ridges, the curved blades, the clips that support the blades, all of these would have to be actual 3 dimensional objects, because they all provide silhouette when viewed from different angles. While such models might technically not be that taxing for modern gaming rigs, if you put 40 players in one place all wearing the same armour, the GPu is going to start taking notice.