I found a bunch of hotels for well under $500/night for those dates (I am assuming two people in the room, obviously a family-sized room will be more). We stayed at the Kong Arthur hotel, which is in a great location, very near the Norreport Station. I saw it on Expedia for your dates for $313/night. If you search on trivago, set the it to less than $350/night, reviews of 7.5+, and within 2 miles of the city center, there are a few hit, including Hotel Ansgar for $193/night. I can't personally vouch for that one like the Kong Arthur (which was great, I would absolutely stay there again), but it has good reviews. Expedia also has the four star Imperial Hotel (not far from the train station) for $268/night. The prices I listed are before taxes.