The rampant inflation is extremely annoying. In my view it is not just caused by excess coins in the game, but the greed of peeps in the TO. In fact it is easy to manipulate trade prices by buying all the stock of an item and then selling for a much higher price - how often have you sold an item and then seen it offered for a higher price by the person who bought it off you?
The current set up of a players setting the asking price in the TO leaves open the possibility to just keep asking more and more for items. I have played several games that have the equivalent of a trade office, but none of them have just had player set prices.
My suggestion would be to change the TO to put a limit on the max amount you can charge for an item, either by having 1) a default seller (ie from the game), 2) a set price for items or 3) a range of prices depending on how many of that item is for sale.
1) there is a default shop keeper that sells & buys items at a set price ie sell copper @21 coins per K and buys copper @20 coins per K. Players can then add their own trades, at any price, but obviously they will only sell items if they are lower than the shop keeper.
2) there is just the shop keeper that sells & buys items at a set price ie sells copper @21 coins per K and buys copper @20 coins per K.
3) items are available in the TO, but also the amount available is shown....the more of an item in the TO the lower the price ie if there is 50K saltpetre available to buy then the price would be 500coins per K, but if only 2K is available then the price would be 650 coins per K. The same would apply to selling; you would get a higher price if there isn't much of a resource available for sale.
Option 3 is my preference as it would allow for higher prices for buying & selling at times when items are in demand like during an event where a certain resource is required