That is for the "black cab" taxis, the ones you can hail by waving on the street.
For a private hire vehicle (the kind you telephone or use an app to book), the price is under £700 (under £500 if the driver speaks English).
That doesn't seem unreasonable. The GP comment was referring to the American system where the license are traded at very high costs (tens, hundreds of thousands of dollars).
Those are the prices for becoming a black cab driver (allowed to respond to street hails and use taxi ranks) - to drive for Uber only requires a "private hire driver" license.
The private hire license avoids the need for "the knowledge" and to have the traditional London black cab. There are still fees involved, of course - but becoming an Uber driver is much less demanding than becoming a black cab driver.
