500 NTD or about 15 Euro, queue times are long to buy tickets, then you need to wait until your designated slot to go up, then you queue for the elevator which can take awhile and then you queue to see the city. Then when you want to leave you need to zig zag through a maze of jewelry shops and local designs that are not cheap just to queue to go down the elevator.
my idea, if you like this sort of stuff great if you are not really going to care if you get a hazy photo from the 89th floor then google it and save the headache.