Now that you have generated some empty brass, look at how cheap it is to reload the 5.7 x 28mm.
Bullets are cheap, primers are the same, and all it takes is a pinch of powder.
In fairness, some one could reload .223 cheaply also, since empty brass is so much more readily available. The same goes for 9mm, which also enjoys cheap, (some times free!), brass, and the pinch of powder, and can use cheap, (store bought, or home made), cast bullets.
The PS90 has the best brass catcher of any firearm I have ever owned. This also makes reloading a cheaper proposition.