There is a difference between price changes and actual buffs/nerfs to guns.

Both effect metas, but not really in the same way. Let's say the SG is objectively worse than the AK, but it is lowered to $500. Obviously it would be used constantly in a few different ways. It would be used in place of pistols. You now get a rifle on pistol round. It would also be used more when funds are tight. You can basically save while still buying a rifle, to save up for the next rounds.

But that doesn't mean it is better than the AK.Once you don't have to worry about funds, you would still be spending more on the weapon that is better.

Buffs/nerfs are different. If a SG is buffed to the point it is better than the AK, then it would be the go to gun.

Point being, a price change is going to have an effect on the meta, but it is never going to be the tipping point to make something the better gun. When funds aren't an issue, you'll be going for the one that performs better.

Don't get me wrong, I think I'm better with an AUG than an AK. But that is because I'm not a one-tap machine. If I were, AK would clearly be the better option.