Come on, 3 years? Can't spare $20 to buy a jug of SuperTech?
The problem in my case is mostly waste. I try to change oil in all 3 cars at roughly the same time and that means 18 empty 1qt bottles (it's impossible to find gallon jugs for the oils I use) and about 4.5 gallons of "used" oil that I have to go and dispose of properly. From what I understand, the bottles themselves are non-recyclable since they are contaminated with oil.
E39 uses almost 8qts, the VQ in the pathy ~6qts and the Corolla a bit less than 4. That's not counting the 1 or 2 extra qts for the bimmer since it consumes a bit of oil between changes.
What the oil costs is honestly secondary, especially considering that the fact I'm not using the cars has saved me a ton of money in gas and parts.