The value of X should not matter.
While pulling the existing cars off the road in an instant seems to be an expensive and bad idea, I don't like the idea of suddenly caring about the livelihoods of VW employees. We're talking about a Big Co here, the kind that axes thousands of people because sales said they can't meet their quarterly goals.
How am I, as a citizen, ever to trust the government can hold corporations in check, if not just them, but we ourselves hesitate to take action because of collateral damage. No surprise VW is pulling off the shit they are - they know perfectly well they'll get away with it even if it goes public.
Think of every VW, Audi, and Porsche dealership and manufacturing plant in the US being mothballed overnight. Not even mentioning the secondary effects, that's a lot of unemployed Americans that are paying for mistakes made by people they've never met.
And? So the company structures its mischief so that any correcting action will damage innocent bystanders, therefore holding everyone in check. What happened to "America doesn't negotiate with terrorists"?