What all does the Affordable Support upgrade do

Affordable Support 10350 sp (11500 non premium)
-50 cost for all Support units

I guess my question is which units count as support units. At first I thought it was bombers, stealth, transports, helicopters, and sentry planes. But I read somewhere it was only sentry planes. (and if this is the case I don't find it to be worth the price)

Also, if it does indeed affect bombers or air transports, does it work in combination with sky menace? (essentially w/ SM bombers cost 130 but with AS upgrade would they cost 80?)

Thanks

It's only the sentries. You won't need that upgrade right now.