Just some food for thought...
I know the OP question centered around cost, which is a valid point to be sure. However, when to change your oil and with what oil/filter are questions that follow right behind the one of cost. The 4 friends I ride with up here, all have different bikes and we all use (and swear by) different products. We have discussed this "ad nauseam" and are no closer to a consensus at all.
One point we do agree on is you should change your oil at the manufacturer's recommended mileage. Synthetic oil will give you longer mileage in-between changes but originally, the cost is a bit more. Synthetic oil and the proper weight of that oil (something like "Amsoil", "Mobil 1"), is a must if you live up in the frozen north or down where the heat becomes a real issue. This gets into engine "care" as well as "cost". We also agree that if you are going to use "Dino oil" (non-synthetic) and are concerned about engine ware, you could use something like "Archoil" or "Lucas oil" additives. Which gives you better protection but bumps up the cost at each oil change. Most Harley owners (older bikes as well as brand new) are using a Synthetic oil to quiet down some of the engine noise as well as longer life out of air-cooled Vtwins - https://www.harley-davidson.com/shop...il-change-kits
. To my one friend, (who has money) cost is not an issue, engine protection is tops on his list. To another friend of mine, every dollar counts and he puts the cheapest oil/filter he can find on this bike.
Hold on my head is starting to hurt from all of this!
Whatever you choose to protect your bike you should be religious about changing that oil/filter, plugs, air/carb filters, to give your engine the best care so it will give you years of service.
My father used to tell by brothers and I about caring for machinal things (car, lawn mowers, whatever) "If you take care of it... it will take care of you." I have always tried to live by that advice and it has been great advice.
Like is said, just some food for thought.