Depends where and what exactly you're doing.

Based on someone else's post, the land value alone is far higher than the total inflation adjusted costs.

As for how low the cost was, we'd need to see what they produced there, versus what parts they bought at other places and assembled into a product at that location.

It’s pretty cheap to build a factory when it basically a building with some tables inside

Perhaps, but CRT manufacturing is far more sophisticated than that.

Do it in China. It's way easier and faster. Guangzhou has like 15 manufacturers who can build CRTs for you with delivery mid-Feb. You'll have to do QC, though, because they have al sorts of image issues. But I think it would be way easier to get one of them to be good (for a price) than to build these yourself unless you're already an expert with access to the facilities.

Oooh – I need to find a replacement for "standard" 9" tubes, for both industrial hardware and for compact Macintoshes... do you know who they would be?

This was also a time when vacuum tube electronics were still ubiquitous, so there were probably a lot of things that were common back then that aren't available today. Not to mention domain expertise and workforce.