In addition to the public shelters established by the officials in Pengcheng, there are indeed, though few in number, private sanctuaries like the one built by Dong Tianyu.
Initially, these sanctuaries were created due to rumors of the end of the world. The apocalypse didn't happen, but the era of online stardom came.
They originally relied on live stream donations to get started on the construction, then adjusted their approach in the era of short-video to pursue popularity.
When the popularity of short videos declined, the era of pandemic came once again. The sanctuaries were taken over by the rich, who initially believed in the apocalypse, for yet another round of upgrades.
The overall cost of constructing these shelters may not be higher than the cost Dong Tianyu incurred in carving his sanctuary out of a mountain.