tigerdirect has 30-packs for $9.99 ($17.98 with tax and shipping)
Go to a PC Shop, -but for a pack of 50 on average a £10.
How much you pay for a package of CD-Rs is dependant upon a few factors: how many you are buying, the brand, where you are purchasing from and if they are on sale or not. As of writing this answer...
about 6 euro
$10 - $20
DVD-R should roughly sell for 29 to 39 US dollars per spindle of 100.