Once you've taken into account the cost of the blank labels, I think it's still cheaper per disc to buy injet printable ones. Most labels work out at about 15p to 20p each.
There's a whole load out there. At work we use HHB ones becuase they're pro, and we get them for less than 30p a unit (mind you we do order 10,000 at a time!) but they're as good as you're likely to find. There are cheaper options available. Verbatim also do a printable surface disc,and I've seen these but not tested them....
http://www.ishop.co.uk/ishop/883/shopscr206.html where they're about 27p a disc.
The big advantage of printing onto disc rather than labels, is that many labels cause compatability issues when playing, particularly with slot inserts and in high speed drives. The labels can cause inbalanaces causing read errors, plus in some cheaper cases the labels will peel off, or the chemicals in the glue can damage the disc.