Buying heart worm/ flea wormer at vet you are paying top dollar. I get all mine from mail order company's cutting out the middleman
When I went online to get the Rimadyl for my dog, my vet had initially directed me to their website, which leads you to another portal where you can purchase meds from an online store and have them shipped to you. She told me the website would contact them to complete the Rx paperwork, which sounds upfront like a good thing, that they are going to handle it all for you. Well, I compared the prices of both the Rimadyl and Carprofen (generic by Putney) with 1-800-Petmeds and Petmeds was slightly higher than what the vet site had on it, but they were cheaper on the glucosamine supplement and had free shipping too.
So that sent me looking around at OTHER pet medicine websites online and I was absolutely shocked to find the same meds (both generic and name brand) nearly
$30 cheaper with a couple of other vendors. There were other sites also just as expensive too and it seemed to be the ones like 1-800-Petmeds that I have heard advertised so often were the ones that cost more.
I eventually went with Valley Vet because I have ordered horse supplements from them before and they have done good business. I knew the vet had a high markup on everything you get there at the clinic, but I was just shocked by the differences online as well. Ridiculous. I have had a hard time keeping my two cats (plus the stray kitty that adopted ME) on Revolution. It is so expensive at the vet, $16 per dose. I was pretty upset when I realized that it didn't stop ticks either. So I've since gone with a generic version of Frontline Plus that you can get at Walmart for $24/3-pack for cats.
Frontline suddenly quit working on my dog and I have yet to get to the bottom of that. When Interceptor quit being produced, my vet said they just weren't making it anymore, but I found out later that there were health issues/deaths being reported and it was pulled. Heartguard too. My pets have been on all of them at one time or another. The vet is not very forthcoming when it comes to meds and charges too much. Now that my dog's skin cancer tumor has been resolved, I am going to switch vets because I don't trust this one anymore and I am beginning to think that many of them are just in it for the money they can make off of selling meds and requiring unnecessary costly tests before prescribing them.
Sorry, that turned into a bit of a rant.

But my point was, look online to buy pet medications. The vet charges too much!