Image from Pinoy Atheist
I am sorry but there is a cheaper way of dealing with pests in our beloved pets. It's called fipronil and is the same chemical found in our expensive Frontline or what have you.
You can actually buy a big bottle (about a liter) and dilute 20% od fipronil with 80% cooking oil (yes cooking oil but use vegetable oil and not olive oil)
Is it safe for pets? Of course its in your frontline. Where can you buy it? Amazingly in agricultural stores because the chemical is a good pesticide. I also use it to get rid of roaches and ants and other insects at home.lif