The electrocd.com cart offers for a limited time “recursive” rebates (using the triangular number series) starting with the first disc!

While the first item gets a $1 rebate, the 2nd item gets an additional $2 rebate (for a cumulative of $3 off); the 3rd gets $3 off (for a total of $6 off); the 4th gets a $4 rebate (for a cumulative of $10 off); the 5th gets $5 off (for a total of $10 off), and so on until a maximun rebate of $10 per item for the 10th (thus a total of $55 off) and above.

Try it!