is really not more expensive than Windows software. Not the good stuff anyway.
There are currently no virus's, in the wild, that attack OS X.
If you feel the need for AV software, consider ClamXAV, which is free
I am considering buying MAc after many years of owning PC. I realized that many softwares for Macs are much more expensive than for PC. I have seen anti virus programs for Macs for about 60 $ per year, but do I need anti virus and firewall or new operating system Leopard has it all?