Marginal cost is something that you pay the fixed cost to have the thing that you have.
Examples like Paying for your Electricity, your rent in your house, water and communication.
In the early 19th Century, The First Industrial Revolution shows up and people invent new kinds of Energy, Communication and logistics like Coal, Steam power printing and railroads.
When you write a letter in those days to someone, there is a cost to deliver it but nowadays when you have a phone which is a fixed cost to buy it and once you have it, you write messages and deliver it for free with the help of Internet.
When the Internet is evolving and upgrading, the cost is getting lower and lower that’s why phones are getting cheaper and cheaper.
I write this blog post for free and the cost that I pay is a device and Internet to keep me powered up.
Mark Tacastacas 