Sig Sauer P250 price?

I want to buy a Sig Sauer P250, the one that you can change the caliber, and I want to get the .45 ACP version and also the 9mm version. Since you can change a few parts and get another caliber, what is the best/cheapest way to get one of the full guns AND the X-change kit to turn it into the other caliber? Example: Buy the .45 ACP version and buy the kit for the 9mm, or vice versa. Also, when you buy the kit to switch calibers, does it come with all 3 sizes (Full, Compact, Subcompact) or just one that you choose?