While I´m not a person to spend that much for a bottle of rum (not a huge fan of spirits in general), I´ve most commonly seen people drink expensive rum straight as it is or on the rocks.

Generally speaking: The sweeter/fruitier the drink/cocktail is, the cheaper the rum can be.

While coke contains a lot of sugar, it´s obviously not fruity, so one does notice/taste what type of rum was used (unlike a fruity rum punch, for instance).