I wouldn't buy other than MB for stuff like tie rods, discs etc UNLESS I was upgrading the system.
There are item that other Companies make, that MB put an additional mark up on (Compressor oil for example).
Now, if extra analysis, quality assurance has been done I might accept the mark up.
But I suspect that it hasn't.
If it had, MB would be jumping all over themselves to justify the higher price.
Such things aren't copies/fakes.
They are just rebranded to MB.