What I don't understand about this is why are you complaining? You don't have to accept their offers. Would it be better if they just didn't put up any offers at all?
I'll state some of the cases when such offer can be useful.
1) A guy wants to loom one of those items, then he sees he can get the same by spending 5-50k gold less, he would do that by accepting the offer.
2) Other traders can see what items these guys have and offer an exchange.
I've done a lot of trading so I have some experience with marketplace. The truth is, any offers are useful for marketplace and playerbase.
PS: this, of course, doesn't go for the offers like "+3 item for 2 lps + [more gold than a loompoint is worth]", but I don't really think someone would ever accept it, even being a noob.