it REALLY is tough to justify $900 for a polymer pistol no matter what the situation is.
It's tough for you to justify that. I don't justify it. I simply make the purchase.
If I'm rationalizing, I probably shouldn't be buying it. I own various HK handguns (and rifles) not because I justified or rationalized them, but because I decided to buy them. I haven't regretted them. I shoot them, and I carry them. It wouldn't hurt my feelings a bit if they were the same price as a Glock, but none of my 1911's are the same price either.
Polymer...steel...who cares? It's reliable.
Is HK the be-all and end-all of brands? I don't know. I don't care. They do what they're advertised to do. They do that well. I own Berettas, Rugers, Sigs, HK's, Springfields, yada, yada, yada...most of them are just fine. The HK's aren't tough to justify at all, and the price isn't that out of line with other better production handguns.