I personally would never pay that much. That is why you should just buy through meritline. $9 for four disks, no matter what brand it is, that is too expensive!!
It's up to you. Personally, I can't find any place that offers TDK disc at this price, and quantity. Take another look at mertiline.com, TDK discs are 3.39USD each (at 10-pack).
Still costs 2 times more per disc than Ritek.