Jaunted.com has put together a useful reference chart for Airline WiFi costs and availability. Check it out. Here’s a quick snap-shot but make sure you visit www.jaunted.com for the latest and greatest.
Kayak has an excellent reference for fees across all airlines which is updated on a regular basis. I’ve attached a snapshot of the table as an example (Click on the thumbnail to get a readable picture).
It’s always a good idea to stay up-to-date on the fees so you can make the right decision for yourself and your clients.