I have to say, I think the prices of those things are ridiculous and the flow rates, where they do quite them, very optimistic as well.
I have seen YT vids of them pumping before and for what they are and the price, I really think they are taking the mickey out of people who buy them.
It's one thing to invest in decent equipment, it's quite another to get blatantly ripped off.
They just use modified vehicle oil pumps, I think Fords, so they are nothing specialist nor do the job any better.
They use mains powered motors yet still my battery powered scooter motors I use on my pumps will eat their output for breakfast.
I also strongly suspect they have followed the design of my pumps because years ago they were just tapping into the original port of the pump. Now they are welding in 1" elbows same as I have done well before they started with their original design.
Any gear pump will do the job of pumping thick oil. Does not have to be anything special about them.
I did once have a play with those hand cranked pumps. They have a large roror/ vane inside which is good for oil and they are also positive displacement in operation. I believe there is also a twin rotor version that does higher output.
If one were to put a geared motor on one of these things which should not be hard, I reckon it would surpass the performance of my chev pumps given 1" or better size hose.
Even hand cranked, these pumps should do the job on cold oil and are a fraction of the price of those other units.