I have been using either 1 dog dose of Frontline or 1 dog dose of Advantage on two cats and one dog for the past 9 months or so. I get this plus a syringe (which I have learned to save instead of throwing away XD). When I've used the advantage, I find that I have to re-dose earlier than when I use Frontline. Either way, it's under $20 a month (including a syringe) for all of them. Plus, when I purchase the Frontline, I have enough left over that I dose each of my neighbours dogs (2 dogs, one is 18 lbs, the other is probably about 11-13).