Pricing is a complicated formula of powder capacity, powder type, availability of the brass, and projectile. The .270 and .280 are both based off the same parent brass of the 06. Lots of 06 being made so lower cost .270 and .280 brass (just a matter of neck size). 270 and 280 have approximately the powder capacity and bullets a

270 wsm brass is made from the parent of .404 Jeffery and is a rather rare brass so the cost is more because its rarity and its bigger so there's more brass to pay for. 270 wsm has more powder capacity so more powder to pay for.

Projectile for either 27 or 28 are essentially the same as far as materials of copper and lead. Small price differences for similar grain pills.

As far as killin? Thats even a more complicated formula of velocity, bullet diameter, and bullet weight, and bullet construction. Bullet weight and diameter will be fixed and velocity depends on range. Some folks like to use ft-lbs as a gauge but it tells nothing about penetration. Sectional density is a better indicator of penetration as it considers both the bullet diameter and the weight. The theory is a higher sectional density at a given velocity will penetrate further. So for comparison lets assume the same bullet construction is used. At 140 grains the .27 caliber has a higher sectional density than the .28. At 150 grains the .27 is still more but the .28 is getting closer. But 140 and 150 are the high end of .27 caliber weights and the lower end of .28. Each of theses weights in the respective caliber travel about the same velocity (around 2900 fps). So the 270 with its heaviest bullets will out perform the 280 with its lightest bullets. But the 280 can handle bullets of more mass and much higher sectional density. So the 280 can take on bigger critters that have thicker chest cavity with its heavier bullets.

As you creep up the caliber chart diameter it becomes more an issue of pure mass than anything and sectional density dosent matter. For example a sectional density of a 175 grain .28 caliber and 450 grain .458 caliber are approximately the same. But the .28 traveling 500 fps more than the .458 will not penetrate as far. The 450 grains of projectile dominates at this point.