Originally Posted by
sydneyracquelle
Numerous times I have only had to pay one change fee on 2 one-ways.
Same here, but it requires a calling in, getting a competent agent (most are fine for this, but there's always the wild card), and them having to manually process a waiver to one of the PNRs. Also, they technically could enforce the double change fee if they really wanted to be a jerk that day.
On a single round-trip ticket, you're guaranteed a single change fee and for simple domestic itineraries it can all be done online. Full stop.