I just finished a big expensive bottle of Grand Marnier and found I really can't taste the dif in a Margarita.
Likewise with a small airline size bottle of cointreau I was comparing it to. While both do taste very nice on their own, I would save them for sipping.
Bols make a very nice triple sec that does not have the artificial taste of most of the American brands. It even says on the bottle that it is made from Valencia Oranges, Curacao Oranges, and Lemons.
It is $7 for 1.0 Liter which is less than a third of the price of GM or Cointreau. I even sipped it solo, and while it did not have the complexity of Cointreau or GM it had a very pleasant orange flavor.