My take on this is I understand all the work that goes into design as I have friends in industries who make items that take many hours to design.
Cost of materials aside, one thing not having much light shone on it is the amount of hours one, two, or more people put into the particular design. I do not know off the top of my head what any kind of machinist/machine shop charges per hour, or mechanical designers charge per hour, although I am willing to bet in USD it is between $60-$140/hr depending on where such shop is located.
That said, for a mod that sells for $250 retail, and 1000 were made, that is $250,000 total. I am not a business expert though figure some basic math and think about the time put into design (and don't go and say "its just a tube"), add in cost of materials, packaging, distribution, etc. and you end up with whatever figure going as profit to the manufacturer after all of those costs are subtracted from the first large number seen above.
On a side note, I was speaking with a mod manufacturer, and he actually told me that his particular company starts with not copper tube, but rather round copper stock, and it is drilled out to the desired ID and then tapped for the threads his design calls for. Last I checked (oh, a few days ago, being a plumber and all), a stick of 3/4" (closest to 22mm) type K copper (thickest wall), only sold in 20' lengths, sells for $80 to the trade (plumbing). That is $4 a foot. For 3/4" pipe. That said, imagine what solid copper stock (of similar OD) will cost (or research it online, I am too lazy).
Keep in mind the manufacturer's machine shop does recoup a little with the drill shavings in this case, though the price paid for recycled scrap copper does not come anywhere close to what is paid initially.
That said, I work my .... off to make the money I make and I choose to buy authentic simply because I understand what I explained above, and cause I want to.