Employees are not getting a car for less than the it cost to make the car. They do often get a nice incentive to buy them though. And to be honest, if you manufactured cars for Toyota, you would probably buy a Toyota. If you worked for Ford, you would likely buy a Ford.
As to sales staff leasing, I have seen quite a bit of that as well. A lot of them seem to drive brand new cars for about 6-12 months on a short term lease and then trade it back in for another brand new car. I dont know the numbers behind it, but they seem to do quite a bit of leasing, from what I have seen.