mayrhofen-plattenkogel taxi?

staying in mayrhofen in 3 weeks and in the past have used the train/bus to get to zell then skied/boarded over to gerlos. this year we would like to go a bit further over to plattenkogel and make are way back on piste. i know there is a bus there but it takes an hour. there are 5 of us , so i wondered how much a taxi/mini bus would be . anyone done this who has an idea of the price?