Mr. Roy said himself , that the 257 wetherby was his all around favorite deer getter. If you look at the ballistics of this thing, out to 500 yds, nothing drops less, for regular round rifles, Not even sure a 408 cheytac, 50 cal, or 416 barrett drops less.
But your theory is right, 264 winmag ammo has just got to be cheaper, and if you shoot, say , 10 boxes a year, it may be worth it, if you like to go to the range, and paper punch. but if this is strictly a hunting deal, I don't know if I would do it. the 264 winmag is a very interesting, and underrated round; the peeps who invented it, claimed they did it, to purposely outdo the 7mag, in a smaller action, smaller case, smaller powder amount, etc., and then after 400 yds or so, have better long range ballistics. Well.... they were right, and they succeeded. but the round got off to a bad start, and I think this was a deal were remmy , who first made the round standard, pulled the same crap with this, as they did their fine 6mm remmy round. Plus I think the initial rifle for it, had some probs, so it never caught on like it should have. But in the end, they set out to accomplish beating the 7mag, especially at long range, with a smaller action, and less materials, and they did.