Buy in bulk
There are several factors behind the variety in prices for recordable CDs. As with most things, buying in bulk will save you cash. CD-Rs packaged in spindle stacks will cost less than the same number and brand of discs sealed in individual jewel cases.

Color choices
Blank CD-Rs are available in other colors besides the standard silver/gold or blue-green. Black, purple, red, silver, and other colored CD-Rs look cool, but they can cost twice as much as their generic cousins. Colored discs are perfect for special projects but generally cost too much for everyday use.

Quality vs. expense

CD-Rs, by their very nature, are tricky things to manufacture. Quality discs are crafted with care using high-grade materials and this translates into a higher cost per disc. Likewise, manufacturers who use cheaper materials or techniques can pass these savings along to the consumer.

The bottom line
The average lifespan of a recorded CD-R is estimated between 30 and 300 years. Considering that the information stored on CD-R will likely outlast most of us -- buy cheap and buy often.