I am not sure what you mean with pennies, they charge the same as AWS, and Dropbox just showed that doing everything inhouse saves them millions of $$.
What is the measure you are using for Dropbox being one of the largest companies in the world?
In the beginning of 2017 Dropbox claimed a $1 Billion dollar run rate, however at the end of 2017 Dropbox had a net loss of $110 Million. When your entire year is a loss of $110 Million, saving $75 Million is very important to the companies survival.
