The 4th one, in Germany, took 2 years.

Gigafactory Nevada notably became the second-largest building in the world (by volume) and was a joint partnership with Panasonic, locating two major manufacturing facilities within the same structure. Seems like a big project with additional joint partner complexities.

Gigafactory Berlin is a different beast and produces a different product mix.

Gigafactory New York produces photovoltaic cells and Tesla Supercharger assemblies but does not produce batteries or vehicles yet another product mix.

Giga Shanghai just does final vehicle assembly (basically the easiest kind of factory and most minimally regulated) and is a million square feet smaller than the other factories and with no joint partnership/co buildout.