It's not *that* good. It's cheap as you note - so you will see a number of cities with a bunch of them starting out. But the stages will eventually get replaced as they get better things. And already well developed cities might not bother with any.
It's also quite strongly dependent on age. It improves drastically from FE to SAV (1% per age vs 1% per 2 ages prior to it) - so in SAV it's semi-competitive boost-wise even if the other stats are crap; but back in industrial it's below pretty much all the good multipurpose multi-levels in attack boost efficiency as well as behind on other stats.
In SAJM:
- Winner's plaza Lv 2 is best as a pure-attack building (just pulled ahead of fall set with the most recent +1% in SAJM)
- Fall Set remains the best semi-balanced option (only a little behind winners' plaza in attack but also gives some defense, FP, goods)
- Eagle Reserve, Governor's Villa, Great Wheel, House of the Wolf, Pirate's Hideout provide similar attack efficiency - but also much better other bonuses making them overall much more efficient buildings
- there's other low-attack/non-attack grand prizes that also outrate it for a player who wants more than one thing
The danger of an "optimized all-stages city" is nonexistent
But you might see a few of them for people looking to shortcut buy their way to an intermediate city.