Currently the markets only serve to make the improvements. To sell and buy are not usually feasible. When buying, a devaluation or an inflation in prices is always generated that is never recovered. I propose that like African cattle, prices are readjusted over time, and that the ‘Advanced Market’ card accelerates the process.
The ‘Advanced Market’ card, in addition to your current benefit, you could also make trading positions give you slightly more resources.
In case of having commercial positions, either in the route or in native settlements, it could make the values reestablish more quickly, and they are a little cheaper when you buy, and more expensive when you sell.