system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is "Economics of Scale" ?
gpt
Say that you want to make a chair from scratch. You would need to buy tools such as a saw and enough wood and glue etc to build that one chair. 

Now imagine instead that you wanted to build 100 chairs. You only need one saw and chances are that the lumber yard will give you a break on the price of the wood because you are placing a big order. Same for the glue and other materials you might need. 

Divide the cost of building 100 chairs by 100 and the answer is less than the price of the first example where only one chair was built. 

The idea that it is cheaper to build or make a whole bunch of things is called "Economy of scale" because Economy means "cost" or "money" and scale means "how big" or "how many".