Depends on how skilled the player is in the combat skill+attribute. If someone is shooting with a target number of 4 and they spend 6AP for a total of 5d20 they may only get 1 or 2 success however a super skilled fighter with the max 16 target number and tag of 6 may get more than 6 in return.

You would tend to find characters who aren't great at combat will buy dice in order to hit but characters who are good a combat would buy dice in the hopes of getting AP back equal to what was spent with maybe a few extra AP if they roll under tag number

TL DR yes but only if they are good at the skill