First, Bloomberg's code base represents decades of cumulative institutional knowledge. That's both the downside (it looks 30 years old) and the upside (it's been thoroughly tested and users know what to expect).

Second, for Bloomberg's target customers (big banks, big traders, big hedge funds), the price is just noise in their budget. If you had a "cheaper" Bloomberg clone, you might get more customers but less total revenue. The people who have been trading for 10+ years and know Bloomberg terminal by heart will still want a Bloomberg terminal.