This isn’t strictly relegated to cargo bikes as per bicycles. Bicycles (normal) are also oddly expensive new. I mean sure, you can get your local equivalent of a walmart bike for the local equivalent of $100 but it’ll kind of suck a lot, mostly because it’s overloaded with features and parts that will fail and be somewhat expensive to replace.

At some level I think comparing new cost of cargo bikes to everything else is also sort of an odd deal, an Urban Arrow is a premium cargo bike, an equivalent car costs anywhere from $60,000 upwards to $200,000 depending on where you want to draw the line. That said, bicycles are still very much oddly expensive, even if just compared to how much raw material you get out of like a dacia sandero vs. an urban arrow.

Theories are abundant. Me personally I believe it is both that nigh nowhere in the west has the stranglehold on politics that car companies have and that give them direct and indirect subsidies in a similar amount, but also: I don’t think anyone’s really done the ford factory of bicycles yet. There just isn’t a plant cranking this shit out all the time. Euro Big Box Store Decathlon probably gets closest, but even their cargo bike is comparably expensive. Maybe that’s a time issue, they’ll sell you REALLY solid normal bicycles at very reasonable prices for what you get.

EDIT: There’s also probably some regulatory fuckery going on. You can get, in europe, a chinese EV cargo trike like a Volta VT-5 for 2000€. It’s legally a small motorcycle, carries way more than any cargo bike and also beats all of them on price. I know for example that in germany, bike lights have to be individually approved by the federal car agency, while for anything for engine powered vehicles a EU self-cert is fine. I assume similar things happen elsewhere.