[Magwart]

You can get Advantage II (for fleas, not ticks) for around $10/month through the big online retailers on sale. Watch for sales that can be combined with coupon codes at KV Supply, PetcareRX, etc. It works.

I do not use Frontline, as I'm not impressed with its efficacy at the shelter where I volunteer -- it could be they aren't using it right (they use the spray from Frontline, not the tubes), but I have found fleas on dogs treated with it.

In the South, even though my house and yard don't have fleas, they are in the environment -- in my neighbors' yards as we walk past, in parks we visit, etc. Fleas are miserable for dogs and carry diseases. In this climate, the dogs get devoured by bugs. When I lived in California, many years we could go without a flea preventative because I hardly ever saw a flea, anywhere. It all depends on your climate.

ETA: I recently re-priced Advantage Multi, which is both a flea preventative and HW preventative, and it comes out cheaper for me than separate HW and flea meds. It's around $90 per 6 tubes in KV Supply's latest catalog. I'm likely switching once I use up my currently supply. Also, for the sake of comparison, Advantix (the one you priced at your vet) is around $70 per 6 for the large size.