Hey, life's dishonest. I'm going to give a real life example.

I was bagpacking at Tescos and allowed to eat in the Staff Serve-Yourself-Restaurant. I got a jam doughnut for 30 pence. Outside of the Staff area, they would probably be about 60 pence. (For those of you who don't know, cents and pence are very similar in worth.) Its not profit if Tescos sell them at 30 pence. Now, if adverts were broadcasted around the nation telling people that they had lost out on a whole doughnut's worth of money, less will buy it. So, somebody buys a Retired Item/pet primarily to sell, everybody knows this item is ten million, but nobody's going to throw their tu down the drain, so little to no profit. Pretty much the whole transaction will be useless. 

Okay then,

Revision: Search for an item, and you find the prices of the items in the shops world. Location is invisible.

Compromises sometimes make an idea great, sometimes they sneak it from the  original purpose and kill it. This one seems contrived, and I'm not sure what to think of it.

Ok, well here's another thing.

What about item quests? Item quests are pretty frequent sources of income for many users, but they have a time limit. Most people buy things from the user shops using the seach and that keeps tu flowing. However, if they don't know where to buy it from it's useless and the person selling the item may not be on at the particular time you need it so you fail the quest. Since there is a quest limit there would be less tu in the pockets of res users, which means they would spend less. This disrupts the flow of tu and makes the economy worse.