.458 Win Mag has a strong case to support it as a Miser's cartridge.
Maybe even better would be the .458x2 inch American, because you can scrounge dozens of different calibers that can be cut down to make your brass.
But the basic principle is this. If you really are 'that guy', you own ONE gun, and it has to be used for everything. You can load a cat sneeze load under a round ball for small game and birds, or you can dig deep and buy or make 500+grain solids for shooting wayward elephants and RV's.
As an aside, I have pretty good knowledge about what the effectiveness of a .22 rimfire is, and I would place that in maybe second place. It's cheap, you WILL eat, but you will also have to be well aware of time and place, and choose your shots VERY carefully! Elephants have been done (historical record, not me!). RV's are a little harder. Anything lesser, is a matter of timing and persistence! LOL!