Well if someone posted an item for 10million and it is only worth 2million then I am going to undercut with 7.95millions...

It is not rude, and if your speculation has failed on whatever item, then that is just a part of the game also organized trade cartels and the likes where you are only permitted to do that even though you could sell more items quicker and faster, due to eg, having a much better Chain Supply Line or cutting out the middleman by doing parts of it yourself, just means you are more competetative.

am gonna undercut for 50K or more, if the item is not worth it.. if it is flooding the market, even more.