Re: every cent saved counts
That argument is just as effective for cables, except the cable manufacturers often don't have a brand to protect.
The op is right, expecting the cable to be anything other than a basic piece of wire with the right connectors is stupid. Make the £300 device do the job. You can absorb the cost at the device end more easily than with the cable.
Seriously, engineers came up with this design? They're allowed to blindly trust their input? It'll end in tears....