These are specifically not Bills of Material, but general (LLM-generated, it seems) lists of the kinds of parts involved in things. No specific part numbers are indexed, and things like "Bare PCB" are not usefully-broken-down; FR4 is quite different than what you'd use for a high-frequency RF board, so saying bare PCBs are "$1 to $200" is not at all helpful.

I like the idea implied by the name, but this is more like a "Vaguely How Stuff Works dot com" than that.