There is no easy answer. Even with the same airline, the fare rules for a fare bucket (eg B - which is normally flexible economy) could have different change/cancellation fees depending on where the flight originates from and where the fare was purchased.
The higher fare buckets like Y and B are usually the most flexible with the lowest cancellation penalties (or no penalty), but you would need to read the fare rules for that ticket to check what the exact conditions are.
And if you call to cancel, some airlines may charge a phone agent fee to do it. If you do it online, normally there is no extra fee.
Using the airlines website, usually it is pretty easy to find the details on cancellation costs. Or using ExpertFlyer, you can use the fares search and read the Cancellation/Change box.
Why do you need to know this for so many airlines?
I need a refundable ticket to get the Visa as I know my dates are currently in flux.
But, the Consulate people are stuck to their text book and are fine with issuing my visa on a VALID ticket even if I change my travel plans etc after visa is issued. I've shared this truth with them of how my dates are in flux through the entire month that I could begin my travel.
Their consulate in other places accepts ITINERARY / TRIP receipts, but at this particular location have been stuck to seeing an issued ticket.
I don't need all these airlines. These are the OPTIONS available for the trip and for the TICKET SHOW case that the consulate needs.
So, any one of them if I can UNDERSTAND and DECODE, that would be fine with me.