In the Mac Appstore you can find Kaspersky Virus Scanner for €9. On the Kaspersky website, you'll find Kaspersky Security for Mac, for $60. What is the difference between those two, except the price of course?
This is an extract from the product's page on Kaspersky's website:
However, Mac users who want even higher security levels for their computers can choose Kaspersky Anti-Virus for Mac 2011, with its robust anti-malware protection, on-schedule scanning, instantaneous updates and use of Kaspersky Security Network’s cloud protection.
As far as I can see, the Mac App Store version allows you to perform on demand scans only, whereas the standard version should provide real-time protection as well.