FWIW, I got my drum at a wholesale motor oil facility. The drum was $60 but it was brand new, unlined and only painted on the outside. The burn was quick and only took 20 minutes to remove the outer paint once the fire got going. After the burn, I was able to wash the outer paint off with a scotchbrite pad. Could not have been easier. The inside did not have a liner but did have what seemed like a slight oil film for rust prevention. The film was gone after the burn.
There are plenty of wholesale places that sell 55 gallon drums of offbrand motor oil. Most of these drums are unlined. Although $60 might seem like a lot for a drum, the transition from new drum to UDS was quick and fairly clean.
I guess we all have to decided how much we want to save initially. For me, my time is worth more than the hassle of burning and grinding to save a couple of dollars. For those on Long Island, I got my drum from Miles Petroleum in Farmingdale. I think they have facilities in other states.
