Conversation so far:
what is the use of the burj khalifa
The Burj Khalifa is actually a multi-use building that has restaurants, a hotel, residential apartments, office space and is a tourist attraction with its observation decks.
When did the Burj Khalifa open?
The Burj Khalifa officially opened on 4 January 2010.

Question: How much were the costs of the tower?
Self-contained rewrite: What was the cost of buidling the Burj Khalifa?