Both are indeed awesome handguns that make you feel like you're wielding some serious power. My 4506-1 has been uber reliable, is as accurate as any .45acp I have ever fired and is one of the guns in my collection that I will never part with (hell or high water). Prices vary wildly by location and availability (police trades, used guns, etc.), but I have seen a few recently for around $450-500. 645's run about the same. Of course you will pay more, maybe a lot more, for NIB or LNIB since they are out of production.