Lot of reasons - liquidity, risks etc.

But mainly because of something called counter party risk. The caveats of selling a bitcoin on Golix exchange has been stated here: https://news.ycombinator.com/item?id=15627972

So the inflated price is in lieu for the risks someone is taking to withdraw from the exchange.

At $50 a day, it will take more than 8 months to even cash out a single bitcoin. By the time someone realises the mistake, the price might have jumped to 15k USD.