Heartworm meds- you can save thousands (if you have multiple dogs like me) ordering sheep drench/ivermectin directly on line and dosing appropriately. Do your research, it's easy if you passed high school chemistry or even if you didn't.
I'm spending the summer in a heartworm area, and my vet would have charged about $50 a dog for heartworm testing (unnecessary since AK does not have heartworm, but protocol) plus I'd be spending roughly $40 a month on prescription pills ordered online, which adds up fast. This is a huge cost savings.
You can also easily
overdose a dog on ivermectin. I've fostered a dog who was blinded (permanently) and neurologically damaged by an owner who overdosed the ivermectin. Most people don't realize it's measured in DROPS, not cc's for a dog. (A vet I know looked at some of the dosing recommended online and it was 1000 times the normal dose for HW prevention. Seriously.)
I would NEVER recommend an average person do the calculation or even trust the Internet to do the calculation, without a vet's guidance. The reason is because of the OD risk. Some vets will do the calculation for you -- farm vets routinely do this for their clients. The risk to the dog is irreversible, horrible damage -- if you screw it up, there's no fixing it!
If cost of HW meds is an issue, you can buy Iverheart pills from KV Supply for less than $5/month. (Iverheart is a generic analog for Heartguard.)
ETA: Administering ivermectin for livestock to a dog who may
carry the MDR1 gene is also not safe. The commercial pills have extremely low doses of ivm so that they're supposed to be safe for MDR1 dogs. If you give a huge dose, you lose that margin of safety, and if you have not tested for the MDR1 gene, you could be in for a very sad surprise.