Wow, surprised. I find duty free at PTY to be one of the most expensive ones-- but I don't buy liquor so that may be where it is actually less expensive. Otherwise, super expensive for cosmetics and electronics.
I only buy liquor there. Never went in any other stores. Don't forget that Duty Free is One Liter bottles opposed to .75. And the prices last time I was there was better than Miami or Europe stores. And with an extra 10% you are even better.