The trade office is cumbersome. The huge spreads (= difference between selling and buying prices for the same goods combination) show that it is also often highly inefficient. Also, as pointed out repeatedly here, some players place predatory trades that seem to be just hoping for accidental clicks. Hence especially new guild members or often confused and scared by the trade office, making trades they regret afterwards.
I understand that BB is unwilling to spend the high amount of resources needed to change that via any market guiding mechanism of their own, so why not use the high level players and open an new avenue of activity: Master trader.
In my experience many high level players are
a) trading only at what they consider "fair" prices, i.e. not trying to take advantage of others and
b) hoarders, i.e. having huge stockpiles of many goods "just in case".
So, why not allow those players to act as brokers (intermediates/market makers) who benefit from aiding the market, not just from selling for a profit? I'll gladly help BB with setting up such a mechanism (being a business professor should help there). It would make the market more effficient, put those hidden resources to use and offer another route to keeping high level players happy and busy. It could be implemented by adding new tabs to the trade office - making it upgradeable (e.g. at levels 60, 70 future levels 80, 90 and 100). If the market were efficient, it would also reduce the problems arising from having many (de fact) currencies in parallel: gems, gold coins, guild coins, star coins, pumkins, presents, Easter eggs, footballs... which so far further increases the lack of transparency of the market.