^You're absolutely right that the limitation in 99.9% of the case lies in the user, I'm just trying to give an accurate comparison, round for round. I know when I bought my last rifle, I was dead set on getting a browning X-bolt, and was trying to decide on caliber. In my case, the difference in price between the two was non-existent, and I decided to invest in reloading, so the difference in price of ammo is also irrelevant to me, thought it likely would not be for someone else. I may not be able to confidently hunt at 500M right now, but I do hope to achieve that some day, and feel confident with the rifle and caliber that I've chosen.
Most of the old guys shooting their old 30-06's will outshoot me with my 270 WSM every day of the week; everything has it's purpose. And BTW, there are infinitely more bullets with better ballistics and offerings in the .30 caliber size then there are in .277, it's only recently that we're starting to see some bullets designed for longer ranges than the 270 win was intended on shooting to.
The thing to keep in mind is, when the 30-06 was introduced in 1906, the cartridge and rifle could probably shoot more accurately then the optics of the day were capable of making use of. They had no intention of shooting at 500 meters, and anyone who doesnt intend on shooting that far (great majority of hunters) still to this day do not need anything more than the 30-06, or 308 Win, or 270 Win. It's only since the development of more precise scopes that people have felt the need to reach out further with shooting, and naturally manufacturers market the hell out of them as being 'better'.