A generic no name 4x media (or anything worse than that) is around R$4,00. A CDR is around R$1,00 (even for good brands).
For comparison, I'm seeing DVD +R and -R in the US for about $0.40 for 4x and $2.00 for 8x.
This reminds me of the maxim, "Never underestimate the bandwidth of a station wagon full of tapes". There's a humorous web page updating this to a 747 full of DVD's here:
<http://www.bpfh.net/sysadmin/never-underestimate-bandwidth.html>