Neato.com is running a Free Shipping promotion until 07/26. That combined with a 20%-off coupon code (DHFR) makes for some pretty good prices on TY Premium discs.
TY 8x DVD-R silver thermal printable - $22.40/100 shipped
TY 8x DVD-R white inkjet printable - $27.74/100 shipped
TY 16x DVD-R watershield inkjet - $26.83/100 shipped
They sell other brands as well, but I usually stick to TY. I’ve ordered from them several times over the last 2-3 years with no problems. They ship from CT, which is a nice change from the usual California dealers since I’m on the east coast as well. Shipping is always fast (this last order shipped within 6 hours of ordering).
(And no, I don’t work for Neato. Just a very satisfied repeat customer. :))