Another weird conceivable case I can think of where a RT is better than 2 one-ways. If:

1. You are booking for cash
2. There is a good probability you'll have to cancel the trip
3. There is little likelihood that you'll be able to use the funds within a year

Then when you pay to revive the funds later, you'll only have to pay $100 for the RT vs. $200 for 2 one-ways.

As things stand now.