Right now Tesla says the whole process can be done in under three minutes, but with changes to the vehicle design, it says cars could be ready to go in less than a minute (a video of the process being done in 90 seconds is embedded after the break). While charging the company's flagship EV on its Supercharger network is free, for now the by-appointment-only swaps are promised to cost slightly less than a tank of gas.
When they were introduced, the suggestion was a $60 - $80 price range, but even with the price of gas falling, that may have changed too. The point of the pilot program? To figure out if the demand for battery swaps that cost money vs free charging is high enough for the idea (and the $500,000 facilities that make it work) to make sense.