What’s the problem with that? In my previous team, we had a structure with four levels of nesting where we only ever needed to query the first two levels. At first we used Postgres with normalized tables, but it was just slow as hell. Switching to MongoDB actually made our performance issues vanish.
Of course it all depends on what kinds of queries you need to run, but I don’t think that large JSON documents are necessarily a problem.
Bulk shipping requires storage and logistics infrastructure. Either way Temu and the likes will also be hit by increased costs, though I can’t say if the impact is comparable.