I one has multiple engines using the same oil, then yes its worth it to buy by the drum. We have been buying motor oil by the drum since before I was born. You don't need a pump to get the oil out of the drum, we have cradles that the drums lay horizontal on with a spigot in the drum.
As far as waste oil, there are a couple of options, one being to buy a waste oil furnace, two is to call a recycle company (what I do), they come and pump it onto their truck, give me the gallons that they received, then write me a check. The last load was $.85 per gallon. I store it in an old fuel oil tank I have on site with a 2'x3' opening in the top with a rack to let all of the filters drain out completely.
As has been stated, you have to be using enough oil to justify the means.