I think a RTW may be cheaper if you want to go to (say) two destinations and one of those destinations would normally be relatively expensive to fly to ?

For example, HI wants to go to Easter Island. LHR-x-Easter Island vv is most of the cost of a RTW but, with a RTW, you only deduct the mileage required to get to/from Easter Island.

I think you can only get to Easter Island on OW. Any ideas what expensive destinations are possible on *A which would be a good for a RTW ?