You live in America or UK? If you do, there’s a few sites you can buy off, like Rima.com or SVP.
Some people always talk about “best buy” stores. I live in Australia so I don’t know much but places like that sometimes have good deals.
I’d be looking online for some Taiyo Tuden CD-R. Ritek are good also for CD-R, they can also be cheap.
These could be quite good and they aren’t that expensive: http://www.yesbuy.net/ritek-52x-blank-cd-r-cdr-white-inkjet-printable-silver-media.html
EDIT: They are the same price as those TY but beware, the Thermal TY are weak and can be wrecked easily. TY ceramic coat is the toughest CD-R and far better than those weak Thermals.