Why on earth would someone go thru the effort to sell it at cost thought ?

Also you underestimate economies of scale behringer can employ, I'd be surprised if you could get close to their price.

You can look at various DIY stuff and you will probably notice that getting stuff DIY isn't all that much cheaper

I'll throw you an example:

Maths, which Behringer cloned, costs ~$300 fully assembled

Befaco Rampage, which is pretty much equivalent to Maths, costs $185 in DIY kit.

Behringer Abacus is $100

They are basically selling them at price or below what DIY kit would sell, and not that far off "cost of components"