So, for clarity - setting shooter training issues aside (and those are big issues). Are folks concerned about the cost of transitioning to 6.5CM from 7.62 or is it a question of efficacy?
Let's say - that there are approximately as many sniper rifles as M249s in the USMC - that's ~10,000 guns. If each of those is rebarrelled into 6.5CM when the 7.62 barrel is shot out and the USMC pays $2000 a barrel, that costs $200,000 for the initial change over. Let's assume that new ammo acquisitions - etc. has it run up into the $2,000,000 range.
The cost of a single Hellfire missile is $115,000 each, a Predator drone's Hellfire loadout costs the amount of rebarreling 10,000 sniper rifles once...
As to efficacy, the ballistic coefficient of 6.5 is a significant improvement over 7.62, anytime you can dial 100 inches of drop out of a bullet at the same distance, you're cooking with gas. The longer super-sonic range allows a longer target engagement range. The cartridge itself weighs less than 7.62, so you gain ballistic efficiency and weight efficiency, not too mention longer engagement ranges and better terminal ballistics within engagement range. That all = Better.
The costs associated with this switch are really miniscule. And in fact, are best done in this fashion, where everyone finally says, "You know, 6.5CM does what we need from a medium-sized cartridge point of view, better than 7.62. Yes, we lose barrel life, but realistically, we gain so much. Plus the costs of using the SOCOM supply chain and top-down approach, saves us money spent in in farcical ways like the MHS. We just get what we need and start dolling it out and let everything trickle down as necessary. No long-drawn out selection process that allows superiors and politicians to be swayed by companies and results in selection of an inferior product based on bean counting."