Well, Fairphone had a cost breakdown available for the Fairphone 2 (when it initially cost >500 EUR) …
Here’s an interactive version, too:
https://www.fairphone.com/en/how-we-work/cost-breakdown/
Why not wait until they have the cost breakdown ready for the Fairphone 3?
(I would be very surprised if they wouldn’t do it again.)
Until then, the only thing one can really say to all those “Why is it so expensive?” questions is … Think the other way around: How can your so-called “normal” or “standard” phone be this cheap in comparison?
Hint: It’s not only the larger quantity. Somebody along the way pays the price you don’t.