Hi, I’m also curious, and stumbled upon another option.
From Postnummerservice you can get a shape file with the geographic area of all swedish postalcodes. Note that this only includes postal codes that are linked to a geographic area, but that seems to cover most of the described use case. Sligthly less expensive too, at 6000 SEK, ~ 520 EUR.
https://dev.postnummerservice.se/en/services/reference-data/swedish-gis-geodata/swedish-postal-codes-with-centerpoints-5-digit-level
Swedish postal codes are revised annually, around March. Normally mostly minor adjustments though, so you can perhaps get away with using that file a few years, if you’re not too particular. At least if the license terms allows it, haven’t checked.
The last few years, there has been a push to require public service authorities, like PTS, provide their data as open data. Management of the postal code system has been delegated by the PTS to Postnord AB. So it is not clear to me if geodata related to postal codes and addresses will be made public under an open license compatible with OSM.
