Kael said:obelisk: +3 culture, -1 gold
market: +3 gold, -1 research
elder council: +1 research
market is a netto gain of 2, same is true for obelisk.
elder council is only +1
So if a build a market I get three gold which gain cover the costs of three to research commerce.
So a market worth 3gold if you dont research anything (rate 0% because you want to upgrade your units for example) and is worth 2 research (research rate 100%, more than 3 cities) because you dont have to drop your science rate. Its not really good IMO that a building which gives money is better for researching than a building designed to improve research.
I hope this explains why I think that elder council should be 2 research (than at least it would increase your science output by the same amount market does).
But a differnt thing:
Siege weapons are not really usefull now and still require a building which does nothing. What if you give siege workshop a + to production?