I tested harbor & palace as the MR, it takes too long time to get benefit... MR have enough money to build very many greatworks, and the greatwork is not such expensive(but hard to get benefit), I thought it's the capitalism works in a medval game.
Harbor gives about 160 trade values, it needs one century to build it, cost about 10k golds, it never benefit from 160 trade values for short time run! Extra 260 trade values gives about 50 golds tax every year, it only benefit 769 starting games with 400 or 500 years run. Normal tradepost costs 3k golds and offers 100 retinues cap and 100 golds per year.
And the palace gives 1000 retinues caps , that's cool, means nearly 10k retinues cap with lv 6 tech, but it needs lv 4 keep tech to build... If I can play such longtime to have lv 4 keep tech for every realms and lv 4 greatwork status...
I can have about 180k retinue caps with 100 trade post & Germanic Faith & lv6 military organization tech, after playing MR in 70 years, so it needs another one century...
Harbor needs very long time to benefit, palace only for the poor feudal Governor, which is lack of retinue caps.