There isn't one you have to pay for whatever tour you're going to
https://howecaverns.com/howe-caverns-pricing/ Pricing is dependent on age and tour chosen
There is a parking fee of $2.00 and then you have an entrance fee to get into caverns. (About $25 each adult and less for seniors and children). There are other things to do and they are additional.
Bring a jacket too, it gets chilly down there
Thanks! Your answer is awaiting moderation.