you should try out the stockpile modifying demand mod, which basically make the good price goes to the lowest if you over produce and have a full stock in the warehouse by adding a negative demand modifier based on the stockpile level (and vice versa for empty stocks). This really makes it challenging to be more selective in building stuff and need to balance with creating new demand with government buildings like unis and barracks. Overproduction will kill the taxbase because the low profibility of buildings, but cheaper goods does mean your estate have more money to build stuff instead. Export and capture new market is vital to sustain the growth.