An article in "Flight" a few weeks back looked at COIN roles and referenced a USAF study post ?Korean War? which showed that the COIN ircraft (principally the Skyraider) was 10 times as effective as a jet at a fraction of the cost. Trouble was the loss of crew was a lot higher......
so you have a choice - very effective cheap ground support is possible as long as you can put up with the casualties,................
I'm sure the guys on the ground would suggest losing a few pilots is a small price to pay to save a lot of infantry but I'm not sure the USAF sees it that way........