I want to go to Finland to see the Northern Lights and know the specific budget.

Local prices in northern Europe are really high. A meal, if not too bad, can easily cost about RMB 200 yuan per person. If you want to go to Finland or Norway, you have to transfer to France or Germany. A person's round-trip ticket is about 10000. Depending on which airline, there are still many choices for hotels specializing in Aurora, which can be found online. I suggest that you go there to see the aurora, and don't join the group.