There are two problems with the Material Traders' rates:
the up-rate essentially defines anything lower than grade 4 as having roughly the value of a penny dropped on the pavement - you might bend over to pick it up, but you wouldn't cross the street for it. Also, I currently need to trade off a chunk of grade 1 data and it's not going to feel all that different from simply throwing it away;
while I can see some logic to the cross-rate - the devs didn't want us focusing on one method of gathering each type of mat, trading for everything else, then complaining bitterly about the lack of variety of things to do in the game, though even at current rates a meta has developed for data with the Jameson Cobra - that doesn't alter the fact that trading mats across (or up, for that matter) at 6:1 leaves many a player feeling that he bent over at exactly the wrong moment. People play this game for all sorts of reasons, but rarely I think for the joy of feeling ripped off.
The down-rate is actually pretty generous, which is why current best practise is to focus on gathering G5 mats and trade down for everything else.