It looks like the DA2PLCPV is the distemper parvo vaccine. I'm not sure who sets the prices but that vaccine does contain 5 different diseases so I assume that has something to do with the cost but this vaccine is not extremely expensive. Flea and tick prevention have nothing to do with heartworm prevention or any diseases. Just like heartworm prevention has nothing to do with distemper parvo or fleas and ticks. Dogs require a lot of up keep if you want to do your best to keep them healthy and it is recommended that all dogs stay current on vaccinations. Depending on where you live, fleas, ticks and heartworms can be seasonal but it can also be year round. With the shifting of the human population and the pets they bring with them across the country, parasite prevalence is changing and becoming more of a problem (pets bring the diseases/parasites with them). Speaking with a local veterinarian is your best option to learn Midnight's risk factors and what prevention is needed and when. Also, if Midnight is not spayed, I recommend to get that done. You can avoid many serious (and costly) health conditions by having her spayed.
Costs do vary based upon where you live and if you go to a vaccine clinic or not. Information including pricing can be found for the Vetco vaccine clinics offered by Petco at:
https://www.vetcoclinics.com/Otherwise I recommend to call around or look at the websites of your local clinics. Expect to pay an office visit. Most vaccines are priced between $25-35 per vaccine.
Here is a link about spaying dogs:
https://www.petcoach.co/article/spaying-ovariohysterectomy-the-benefits-in-dogs/ I hope this helps and please feel free to post any additional questions.