When Unity CEO John Riccitiello was CEO of EA in 2011, he proposed a monetization scheme for Battlefield where players would be charged $1 every time they reloaded their gun.

https://mcvuk.com/business-news/pc/when-riccitiello-said-battlefield-players-could-pay-1-per-reload/

h/t @beltsquid 

 @b92dcc07 Least exploitative ftp mechanic.