So plugging in to MinMax Gamer's spreadsheet for spire squad size calculations, it looks like the attack-boosting wonders are roughly a wash under that formula.
Chapter 15 city from the spreadsheet, raising all 5 of those AW by 1 level increases squad size from 3175 to 3205, an increase of 0.95% while giving us 1% in increased damage across the board. For my chapter 5 city, it's basically the same, adding 5 AW levels goes from 289 to 293 for an increase of 1.38% (this probably looks worse than it actually is since rounding makes a big difference at smaller squad sizes). Also, that damage boost is additive, not multiplicative for each level, so it's actually a smaller and smaller total percent increase each time as well.
Damage and squad size are not the same thing, obviously and the difference 1% damage makes in a fight can vary quite a bit (if it's enough to one-shot an enemy mage before it gets off a debuff it's highly valuable, if it doesn't increase the number of units killed in an attack or only contributes to overkill on a kill shot it's effectively wasted). But in a general sense, we pay for a slight increase in damage with an equivalent increase in the troop cost of battle.
Of course those wonders have additional impacts - faster training from Needles and VS, orcs from HF, mana from DA, troops from toads. But since the damage looks like it would break even everywhere outside of scouting and completing provinces, there's whole lot less value in those wonders.
