As far as I can tell from Nierle's homepage, they are quite expensive with high quality media such as Verbatim; perhaps they are cheap with lower grade media, but I prefer to buy media I can trust.
If you want quality media at reasonable prices I suggest you also look at WeSellCD (www.wesellcd.com) and IT-Netsupply (www.it-netsupply.com). I am not in any way affiliated with those shops (except as a customer).
You can buy Verbatim DataLifePlus DVD-R and DVD+R 8x at very reasonable prices there. I have bought from both shops and am quite satisfied.
Especially the Verbatim DLP DVD-R 8x burns incredibly well in my NEC 3500. You can currently get 25pcs Verbatim DLP DVD-R 8x for approx â‚¬10 at IT-Netsupply (I can only see the price in Danish currency incl. VAT).