Ask HN: Why is the Metaverse/Quest R&D so expensive?

While I like my Quest 2 a lot and enjoy Horizon Workrooms much more than Zoom meetings, I have a genuine question: Why is the development of it all so expensive?

From what I understand they spent around $3.672 Billion on it in the last quarter alone. It’s such a mind-baffling amount.

Is it the hardware development or the software? A developer/scientist will not cost on average more than 100k per quarter (not year) even in the US, right? So for a billion you can hire 10k people. What am I missing? Where is all that money going?