It was in Verkkokauppa (finnish version of amazon, crudely speaking) in Finland. They were marked as refurbished on the storepage but the boxes came sealed with 4 cycles on the battery and no visible sign of use (I think I ran some utility to check for SSD usage and it was pretty low but I didn't do it immediately after turning on can't base anything off that).

Either apple refurbished a product return and then resold back through Verkkokauppa? The machine came with Sonoma 14.3 or 14.4 which is well after the November 2023 manufacturing date. But sealed box threw me off, cause the unboxing felt exactly the same as for a brand new macbook. Warranty I got from the store is also the same you would get for a brand new item.

nonetheless, the value is great. 24/512 14inc M4 Pro costs 2500eur in Finland brand new for reference and I got this M3 Max for 2999

It's most likely factory refurbished by Apple. You can buy these directly from Apple, and I've seen them in small quantities on third party resellers but I'm not sure how they're sourced.