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.