When beverage cans were initially developed, they were actually more expensive to produce than glass bottles, but over time, the process for can making has become more sophisticated. The current method is incredibly efficient and increased automation means that it requires very little manpower.
The canning process starts with huge rolls of metal in thin sheets. These sheets are fed into a device that stamps them into shallow cup shapes with a press. The cups are fed into another series of machines which gradually use heat and pressure to elongate them and thin the walls. The cans are trimmed to an exact size, and jagged edges are removed. A series of machines wash and dry the cans to completely sterilize them, and prepare them for the next steps in the process.
There is lacquer added to the outer part of the can to prepare them for printing. The cans are then painted with logos, and a varnish is added to the base. After this, the inside of the can is sprayed with another lacquer in order to protect the beverages from metallic interaction. Between each step of lacquering or painting, an oven is used to quickly dry the cans and prepare them for the next step.
The upper openings of the cans are reshaped so that tops can be applied to them. The tops themselves go through a separate stamping process, and sometimes this process happens at a totally different facility. The can and the top come together at the beverage filling plant where the beverage is added to the can, and the tops are immediately put into place.