We joined the Cosmos Central Europe tour in March-April 2012 and the Wieliczka Salt Mine was offered as an optional excursion, paying EUR 40 per person. We didn't regret joining the tour of the salt mine. We've been all over Europe and it was our first experience to be in a salt mine. The St. Kinga Chapel was very impressive with the chapel carved entirely of salt. One advise: you should be able to walk for a very long period of time and be able to go up and down long flight of stairs.