In my opinion...How much psi does the VW Tdi use in the injection process? 20K psi? 30k psi? Bosch has many products that could fit the bill. In your argument of a cheapened design... maybe, but I would say that Bosch would have addressed that by now.
The pump has a materials problem. Steel piston in an aluminum bore yields aluminum bore wear material as being sacrificial, swarf not being magnetic (steel) confirms this.
The pump has alignment problems. The cam follower has no means in the design of staying perfectly aligned with the cam, it's not secured in any manner that will keep it in constant alignment at all times, like a pinned rocker arm roller would.
There aren't enough rollers to bear the load on the cam for the amount of pressure generated, and the one roller being used is too small in diameter, too many rpm's, and is overloaded.
Both cam and roller get galled in current configuration.
Both generate wear materials that rapidly contaminate and destroy and cause destruction and replacement of the whole fuel system, to the tune of $7 to 8000, with parts constantly on back order and a long down time.
If those aren't enough defects to keep folks away from buying one of these, perhaps $3400 turbo failures, $6000 DSG failures, $1800 mechatronix failures, and who knows how much to replace a diesel particulate filter failure.
Most everything about this car is under engineered and not designed to run much more than 150,000 km or 90,000 miles, per volkswagens own statements.