I dont understand why people hate on markets so much.
high hammer cost, the happiness is too conditional and not really needed -- immediately or later on in hammer economy -- especially for 150h for typically 1-2 happy faces, doesn't work on build wealth, increase to yield is dependent on the slider setting, merchant slots mean nothing with access to Caste, and so on.
biggest hit to them is just nothing they add is really a priority from the market itself being the source
at the stage of the game it comes around. HR covers happiness in a pinch at as little as 15h per happy face. Caste is just around the corner for Merchants, if you want them, or something like the GLH may have already gotten you one on some maps. Again, they don't work with Build Wealth which is unlocked by the same tech. The effect the market even has is diminished by running your slider at anything other than 0%, at a point where you are finally likely to stop practicing binary research for the first time. They aren't cheapened by anything like CRE and they come later for greater price with a worse GP slot compared to libraries.
And then later on (hammer economy/factories) the happiness they add is worth even less while the health on something like a Grocer, Harbor, or even the lowly Aqueduct is more attractive than the 150h Market. Barracks in Nationalism is a better deal for additional happiness and pairs with the low-cost civics train (Nationhood+Caste+SP+Pacifism) or as part of a drafting campaign even before hammer economy. And the hammer boosters (forge, factory, power, State Property) have you covered when your mature cities build wealth.
I rarely build them at all, and even then only in space or modern war games where I let the cities idle and build infrastructure for awhile after all the hammer boosters are in place and I'm prepping for the push to Tanks or space techs after.
how cheap would a market have to become in order to transform it into a usually-good building that you'd want to whip/chop in most commerce cities? if it cost 90 like libs would you build it? or would it have to be cheaper?
90h would be okay, but it still wouldn't be competitive with Library unless it still had something more....like a basic +1 happy, or some small amount of static gold generation without the food cost of running a specialist. Libraries are so good precisely because of the access to Scientist specialists, which produce MUCH more valuable GPPs than merchants and even their raw beakers are stronger than the same amount of raw gold that early...and because they come even earlier at Writing on top of that.