The cost of visiting Japan in December can depend on various factors such as transportation, accommodations, and seasonal activities. Specifically, December is considered to be a part of the high travel season due to the winter holiday season, especially with the popularity of Christmas and New Year's celebrations. As a result, you may find that prices for flights, accommodations, and certain attractions could be higher than during other times of the year. On the other hand, many shops and department stores hold year-end sales and it's easier to find bargains. Additionally, there are seasonal activities and events unique to December, which can add value to your visit.
It's always best to plan ahead, compare prices, and consider off-peak destinations and activities to make the most of your budget when traveling to Japan in December.