I don’t have much to add, but apart from Portuguese 1st edition Jungle; Dutch unlimited edition Fossil; and Spanish 1st edition Neo Genesis, I hadn’t seen Korean unlimited edition Base Set being mentioned yet as a crazy rare set. I know multiple species collectors whom are missing a single Korean Base Set card to complete their collections across all languages/variations.
The Portuguese 1st edition Jungle Pikachu was also the last Portuguese Pikachu I needed to complete all 75 Portuguese Pikachu TCG cards at the time, and the only card my Brazilian middleman was unable to find.
I ended up buying three Portuguese 1st edition booster packs from eBay, which fortunately contained two of the Pikachu (and a holo Jolteon). 
This was back in July 2017 (I showed a picture of the Jolteon here), so prices were a lot different than the 800-1000 USD each mentioned above (I got curious and looked back, and apparently I’ve paid 62 euros for the three packs combined - dang I miss my early collecting days sometimes, haha 
)..
Greetz,
Quuador