Other than the "bomb them back to the stone age" strategy and using air cruisers which just plain aren't condusive to life, I find that the cheapest way to deal with them is to use a 2:2:1 ratio of artillery to mech destroyers to strike mechs... if you play as the GE like I do, substitude dark troopers for the strike mechs.
Hope I helped... Thanks for Playing... Peace Out...
"Not everything that can be counted
counts, and not everything that counts
can be counted" -Albert Einstein