There is a possibility to buy both products together with a discount price, but when it comes to online purchasing, you have to add one product to the cart and then another. This is impossible to accomplish as each product is added to a separate cart. So I can’t buy a bundle as advertised on the site. Is there a solution to that?
Besides posting here, you can ask to sales (at) avast (dot) com
I believe there already is a bundle of the Mac and PC edition for sale
Edit:
This page shows $49.95 for a bundle of both Mac and Pc editions
http://www.avast.com/eng/pricelist-avast-mac-edition.html