Billions 
It does for the major car companies.
You have to re-tool big time for mass production. Very large capital investment.
"Tools" in mass production does not mean wrenches and screwdrivers. It refers to all the specialized machines, jigs, molds, etc. used to produce the parts and assemble all the parts in a car. Nowadays many parts are outsourced but they still need to be designed and created.
Specialized machines like this cost hundreds of thousands to even millions of dollars.
This takes quite awhile to put together and get working in a smooth manner for mass production and the resultant economies of scale to take place.
The investment is re-couped by the sale of large quantities of cars.
A "toolmaker" and "machinist" in a GM plant makes these types of machines. It's a specialized trade type of job like electrician.
Imagine taking a GM plant used to make Chevy Impalas and converting it to make Teslas. You'd have to start from the ground up practically.
