I have bought Taiyo Yudens from Rima.com in the past, but i try to get deals locally first, since sales at the big retail stores are pretty much always alot cheaper.
Granted, i work in retail, so i have access to knowing when sales are coming up, & am able to test DVD-/+Rs that we get in to determine who manufactured the discs, but it's still not too hard for even someone who's not on the inside.
Here's a few examples of some deals i jumped on locally in
Cdn. dollars:
BenQ 8x DVD-R 100 pk. - $12 :Q (manufactured by Sony

)
Maxell 8x DVD-R 100 pk. - $40 (manufactured by Maxell in Japan - extremely high quality rated media)
Fujifilm 8x DVD+R 100 pk. - $32 (manufactured by Taiyo Yuden

)
IOW, keep an eyes on those local deals!