I have the Depo shot you only get the shot every three months. As of how much it costs it would range about the same as three months cycle of birth control pills
To get all the information you need regarding the depo shot, click on the website below. If it doesn't work, copy and paste it to your browser. Anything and everything about the depo shot is there. Hope it helps you.
http://www.plannedparenthood.org/bc/depoforyou.htm