The cheapest I have seen them:
$299 for Sonar
$399 for Sonar XL
Once in a while my local Guitar Center has a sale and the prices go even lower.
If you are just beginning, you should check out Home Studio 2002. It has most of Sonar's features (minus some obscure MIDI editing and less DXi plugins). If sells for $69. I have been using it for a couple of months and am very happy with it.
It has the new user interface and supports WDM drivers just like Sonar.
