reduced cost of APC and M-SAM to $600

The GDI APC and the Nod Mobile SAM Launcher are the premier anti-air units that are needed to defend each side from air attacks. Due to the problems of orca spam, they should be given a more prominent role. 
Currently the APC is $700 and the M-SAM $750. This might be reasonable against a small amount of vehicles, but anti-air units need to be able to deal with spam. So they will be reduced in cost so they can be bought cheaper. This is important for the M-SAM especially since it's a dedicated anti-air unit.

To avoid the GDI APC being too good, the damage vs. heavy armor will be reduced a bit more, so it cannot serve the role of "light tank". It will still be able to fight light vehicles well, however.