Apart from making the wrong comparison—if you want to compare to a 270win a 6.5prc, 6cm, etc would be a more appropriate comparison—flatter shooting is more or less irrelevant with a good dialing scope and a laser rangefinder. If you arent on board with dialing a scope then thats on you, not marketing, and there are other “modern” cartridges that would be better choices than a 6.5cm. Truly guys, the people buying 6.5cm for the most part do not give a rats behind that it is slower or that it drops 8” more at 500 yards than a 270. It would be more appropriate to compare a 6.5cm to a 308 or 7mm08.
That some folks want a flat-shooting cartridge so they can use a duplex reticle in a point and shoot scope says more about the shooter than it does about the cartridge. Part of the reason why short action cartridges are popular is because people no longer need such a flat-shooting cartridge to shoot out to what most people consider pretty darn long range.
Also, if you want to look at ammo prices you should be looking at the cost of range ammo, not hunting ammo. Dont know about you, but I fire approximately 500 rounds of range ammo for every round of hunting ammo. All you 270 guys shoot 50 or 100 or more rounds every range session, right?
(This 270 guy does not, my shoulder greatly prefers that I shoot my 6.5 in volume)