OK. So there seems to be a few discussions occurring on this thread. I'll add my comments to each....
Courthouses or Markets -- At Monarch level, and generally striving for a CE with 70-80% research setting, I find the Courthouses a must have in nearly all cities, while Markets get built for Shrine gold multiplier (or wherever my Gold city is) or happiness multiplier.
But on the lower difficulties that the OP mentioned, I can understand why Markets might be better. The city upkeep costs are quite a bit lower, making the 50% cut in city upkeep less impressive. The 25% boost from the Market (even at a 70-80% research setting) could be as good or better.
CoL or Currency -- This one usually depends on which research path I'm taking. Sometimes, I drive the religion path, try to found 1 or 2 religions, build the Oracle, pick a State Religion for production and diplomacy benefits, etc., etc., etc. That makes CoL the first on the list, and I'll trade for the other stuff (like Currency).
Sometimes I completely neglect the religion path, avoid any religions, play nice to most of the civs, work the Math/Currency/Calendar/Construction chain and trade for all the religion techs. That, of course, means Currency before CoL.
Also, map size makes a difference. Many civs, large map, many cities, makes that +1 TR from Currency really profitable. Plus the ability to sell excess resources to a range of needy civs. Since city upkeep costs seem to be adjusted for map size, the Courthouse benefit doesn't really seem to go up. So one might say that large maps makes Currency more powerful than it is on smaller maps.