Must put in my .02 on Justfly. Had booked non-refundable tickets to CCU from IAD - Air India business class. A week before we had to leave - my father in law passed away so we needed to get there within 2 days. Called Air India, they said we would have to contact Justfly. Called Justfly - they charged us $500 but got the tickets changed...everything went off without a hitch and we just got back.
Was it steep to change? Yes. Was it reasonable - Sure! We did purchase non-refundable tickets which were cheaper than what the airlines were offering. I was worried things would go wrong, or some leg not confirmed - but that was one part of the whole 14 days we did not have to worry about.