It’s not a single multi million mega pixel camera. “ARGUS is essentially 368 five-megapixel smartphone cameras clustered together” That’s a 1,840 megapixel (1.85 gigapixel) camera which is not that extreme and in line with several of these images: https://petapixel.com/tag/gigapixel/

A lot of confusion comes because it’s a combination of multiple different cameras than capture wide angles, infrared, and a separate camera that can focus on areas of interest within the field of view. So, if the entire image was at maximum resolution you would get into insane territory, but that’s not how it works.

Obviously the military has "toys" I cant afford, however, do you see any fundamental technologies in that imaging system that are not available to consumers? Even the quoted development cost of $15 Milion are not out of range for a well funded tech startup..