Oil extraction pumps

I need to get a new oil extractor, and I want the vacuum type; I've used that type before and it worked well. However, there seems to be a ridiculous variability in prices! Seago advertise one at around £30; it looks identical to the Pela one at £60! And of the vertical cylinder types, B&Q do one at £35; the Draper one (which again looks identical) is about £70. The prices seem all over the place with no obvious advantage to the dearer one. Can anyone give rhyme or reason why I shouldn't get the cheapest, or is there a good reason to get the higher priced ones?
 
We bought the seago ‘ball’ shaped one just over a year ago, it’s ‘ok’, does the job but found a cheap electric oil pump off Amazon so much easier and quicker.
It now tends to get used more for water which isn’t ideal as the little metal grill that forms part of the pump mechanism rusts. And now I come to think of it, we had to replace the flappy rubber diaphragm after it perished. Maybe it’s best avoided unless you only use it for oil.
 
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