You also seems to forgot that seller have their power too. Transaction are successful when two side (buyer and seller) got agreement.
Selling and buying isn't all about buyer only.

And how did you determine the market price for MSI GTX 970? Did you seen anyone selling this used card anywhere?
General new price for MSI GTX 970 Gaming is RM1,499 and he also bought the item for that price few month ago.
Although some shop selling it cheaper, it also depend on the availability of the product and location of buyer/seller.
If based on your logic, those shop that selling new MSI 970 Gaming for RM1,499 for sure can close shop already because no demand 
There are no single shop in PJ/Shah Alam that selling this card for RM1,399 so it was good for buyer who lazy to go to KL to deal with TS.
His price isn't cheap but i wouldn't call that expensive too. Buyer can always haggle with TS to finalize the deal but don't need to attack his thread and act like price police.
Somemore twist the fact like used Asus Strix price market is RM1,200 and Asus Strix is better than MSI Gaming. I mean wtf is that for.
That totally lowballer buyer with lowballer attitude.

And 1 more, if me as buyer, age of item and warranty play an important role. I'm sure it not just me.
If anyone wanna nego the price with TS, just PM him.