Market Discussions

Item exchange contracts are programmed to enable the trade of items and/or currency for other items and/or currency. A plex for plex+cash fits that bill, cash for nothing does not. The fact that those two are mathematically identical is irrelevant - one fits the system's parameters, the other does not, end of story.

Coding time, which is money but mostly effort going into the un-important aspect of the game.
Changing the parameters can be either something easy, or very hard, depending on how it was coded.
For example making plex behave like a different item might cause other areas of the game to break.

In general, and to refer to your trollish "oh my god" reply. You've got your answer and i'll amuse you for one more reply, one that might fit you silly dancing puppet routine.

1)it was coded like this a while ago without proper thought about scams like these
2)it costs too much time/money to change it when there are more important things to do at the moment.(i.e borken interface)
3)it's coded like this for now, and there's nothing that can be done.

Since we don't know how easy/hard it is to fix it, we can't even say it's something superficial. Programing doesn't work that way.
But you're a teacher, you must know all this already.

/diverts funds and efforts into re-programing a silly aspect of the game.

The contract system was changed to make it easier to use/understand and, probably, to cut down on some of the scamming. The programmer's (rightly) did not anticipate that anyone would want to trade a PLEX for a PLEX mainly because it would never serve a legitimate purpose. If you want your p=p I'm sorry that the contract system does not double as a logic machine. There is no problem here to fix, it works as intended and as needed.

Since there is no item being traded, only a price asked, there is no way to classify the contract in the database. That is, you would not be able to find the contract without an item being sold or requested. If there is no item classification, there can be no contract. To enable your concept, there would have to be a new type of contract or a new type of item. In the former case, it would be beggar contracts, which everyone would ignore, or in the latter case the item would be nothing more than a placeholder, a concept more easily implemented by your using a single unit of some item.