joke?

[wowenglish1]

I would like to know why the next passage is a joke.


A gorilla went into a bar and ordered a whisky. The barman thought that it was
unusual to see a gorilla in a bar drinking whisky and, thinking that gorillas
must be stupid, he thought he would try to take advantage of the situation and
overcharge him. He served the gorilla the whisky and said, 'That'll be fifty
dollars please'. The gorilla immediately took out his wallet and paid the
barman, who was very happy. The gorilla drank his whisky quietly and then
ordered another. The barman served him and charged him another fifty
dollars. As the gorilla was drinking his whisky, the barman got curious and
decided to find out why the gorilla was in the bar. So, to strike up a
conversation, he said, 'It's funny, we don't get many gorillas in here'.
'I'm not surprised with the price of your whisky.' the gorilla replied.

[Anglika]

The joke turns on the gorilla's response to the bartender's comment that he never sees gorillas in his bar is that it is the price this bartender charges which stops them coming to the bar. We all know that gorillas don't go to bars or drink whisky.