I just signed up for a Avast SecureLine VPN subscription on my iPhone and iPad. My question is…do I have to pay a licensing fee for my laptop too? I couldn’t find any options bundling laptop with mobile.
avast is already working on cross-platform licensing, but at this moment subscriptions are per platform.
As Eddy says, unfortunately you have to buy separate subscription on each platform. Cross-platform licensing is planned for the future but it’s not ready yet. At least you can use your iOS license for multiple iOS devices 
There is a real easy way to find out…
Look at the avast website > https://www.avast.com/secureline-vpn#pc
Yes, you can test it for 7 days.
Nevertheless, you’re in the wrong section here.
→ https://forum.avast.com/index.php?board=80.0