I'm just planning to roll out Webroot to my customers and was just curious as to what other MSP's charge for managed AV? I've tried doing some research online but can't find any companies who publish their prices online.

Depends on how nice you are. lol

I have set pricing various ways until i realized I was too nice.  I started by just offering it at my cost, then bumped it up a little to stay under current retail pricing.  Currently I am around retail.

I treat A/V and RMM as tools. I don't make much if any money on the product. I don't lose any either. I make sure I cover my costs including merchant fees. It's when the red flashing light goes on that it becomes profitable.