I am pretty sure the cost of producing the case is a lot less than $800. It's mass produced in China. It will be made for peanuts! Completed for us because we don't make them, but easy for those who do.The raw materials cost is utterly insignificant, sure, but the time and effort sunk into finishing/polishing that watch case is undoubtedly going to be significant. The case is a very complex overall shape, with many nooks and crannies and various holes of different sizes and shapes and so on, and the ceramic material is quite hard (~8 mohs scale), making it difficult to process.
So apart from apple tax, there's a reason it is costly.