AA Guns - I think the price is fine at 5. I still buy them but rarely more due to their limited usefulness than their price. i.e., if they cost only 3 I wouldn’t buy more than I do today. At the end of the day, as written, they are more of a deterrent than an actual combat unit. Want to make them “feel” like they are worth 5? Give them the option of AA fire or a defense value of 2 in each combat. Flak 88s certainly killed enough Matildas in North Africa.
Cruisers - Yeah, as written, there is certainly an argument for reducing them to 11 (though I wouldn’t touch the Battleship cost). They really need something a little more to make them worth 12, whether its the ability to bombard facilities on islands or even an R&D option to create Anti-Aircraft Cruisers that can act as an AA gun rather than using their 3 defense value.
Tactical Bombers - I think they are perfectly priced at 11. Their ability to attack at a 4 both on land and at sea is powerful, arguably more so than the fighter’s ability to defend at a 4. I think perhaps it is only the relative cost of the strategic bombers that make them seem a poor buy.
Strategic Bombers - I would pay 13 for these; I may even pay 14.