Another old thread re-awakened.... I'm not so sure about that, - In China, labour for repetitive ie: 'factory work' is cheap and, (I guess), building rental costs are relatively low... A lot of the component manufacture is subbed-out anyway.... So why rent/build a massive, costly, impressive and tailor-made manufacturing plant when you can keep it rented, small(ish) and subbed-out and cheap? It minimises your risk and investment, no matter how much money you might be making from selling the products.
Here's a link I posted on another DJI factory thread recently, but it's to another drone plant:- Inside DJI Factory - OK, not DJI - but something very similar, and I would guess that it's still not far off the mark of how DJI products are made = a cooperative of subbed workers and factories, working from smaller, separate units to put together the finished products which sell well, phenomenally well, in fact..
Of course, if someone can post a genuine photo showing a massive and high-tech DJI factory, then I will apologise profusely and hang my head in corrected shame at this post..
On the other hand, some manufacturing facilities in Shenzhen are massive and comprehensive, as you can see here, but it's not for drones.