Depending on how soon the stay is, I would book a refundable/free-cancellation rate and watch for rooms to open up more cheaply last minute at this hotel and others around Stockholm that may be considered acceptable. I find award room nights open up rather often for me at the last minute as long as I am flexible about which hotels and have points available in various hotel programs to use to avoid the high rate nights. It may even be worth buying points in some cases. Definitely worth looking repeatedly and even throughout the day of desired check-in to see what becomes available more cheaply or if award nights pop up as available.
Personally, I wouldn’t pay 4600+ SEK for At Six. The breakfast chaos during busy times there is enough for me to not to want to pay even half of that. But if it’s on a rate plan with a $100 credit and really wanting to eat and drink at applicable places at the hotel and wanting guaranteed 4pm checkout — they haven’t always been great about 6pm checkout for Nordic Choice Club Platinum — then I can see why it would be in the consideration if not able to find any other acceptable place. But I would try to avoid getting hit by such a cost to stay at this hotel, but that is as a value-hunter.
