None, if each of the companies were 1/4 of the size.

Not necessarily true. Economies of scale is a thing.

Up to a point. Beyond that point, "economies of scale" becomes "monopolies of scale". Which is Stoller's (and the OP's) point.

This. More, smaller companies mean more duplication and overhead which can manifest in higher prices. One of the biggest factors behind market consolidation and centralization is because it reduces duplication and overhead which can increase margins and might reduce prices.

Merely increasing competition doesn't necessarily drive prices down.

The same amount.

The 4 companies are competing for their share of the existing business

Tell me one industry that couldn’t be chopped up into 4 or more corporations? I think you will be hard pressed to come up with one.

EUV machines. total demand seems to be <20 per year and developing each generation is a billion dollar effort