I noticed that problem too, as said currently there is no sense at crafting sniper bullets via F9 since it is cheaper to buy it.
Increasing it to 15 from 12, won't gonna hurt anyone besides that this will encourage people to craft it. This will increase demand for Iron little bit which is good for CIT economy.
I don't see a problem here so about reasons I stated above, supporting this.
Also not only sniper bullets have this problem, currently crafting ammo of deagle,combat shotgun and country rifle is way more expensive than buying it.These are should re-balanced too.
Country Rifle
35 bullet for 100 Iron and 3 Explosive which cost nearly 2450$ at the current economy.
So it costs 70$ per bullet to craft while it can be bought from 50$ from ammunition.
If it adjusted to 50 bullet per crafting, it becomes 49$ per bullet which is balanced.
Combat Shotgun
50 bullet for 10 Oil,50 Iron,4 Explosive which cost nearly 2410$ at the current economy.
So it costs 48$ per bullet to craft while it can be bought from 40$ from ammunition.
If it adjusted to 60 bullet per crafting, it becomes 40$ per bullet which is balanced.
Deagle
60 bullet for 100 Iron,4 Explosive which cost nearly 2800$ at the current economy.
So it costs 47$ per bullet to craft while it can be bought from 30$ from ammunition.
If it adjusted to 95 bullet per crafting, it becomes 29$ per bullet which is balanced.