My comment is not what the typical customer wants to hear but I have purchased thousands of binos (for shops...) and visited 2 factories, so I am a bit aware of what happens at the source.
That is why we need to be cautious when looking at very similar items at widely different prices. They could come from the same production line but simply have failed to pass the test...
You would be surprised to see how many brands are made on the same production line.
Franco