My yorkies go through about 2 bags of food a month which is $14 something or other
Then their shampoo, which I bath them once a week and one bottle lasts me about 2 months. Their heartworm meds which I get for a decent price... and then flea - flea stuff is what is the most expensive 
umm if you break it down It is under $100 a month, probably more like $70, plus any treats and special toys we might get them in that month. 
BUT lemme tell you, that just in this month we spent almost $500 at the vet. That of course is pretty high, and most was on one of them that was sick and included things like rabies and heartworm tests for both dogs and some take home meds, and a check-up and a REcheck-up.  
So it isn't really the months expenses that get you, it is those surprise things 
