The accounts in Swiss banks will be taxed at between 19% and 34% by the Swiss authorities on the principalsum, depending on how long the account has been running.
In its Victorian incarnation, a tontine was an investment pool to which a group of speculators contributed capital, the principal and interest to be distributed in a lump sum years later to the last survivor.
Of course, lenders are quick to point out that escrows are not actually a cost since they are just establishing the escrow reserves to pay your taxes and insurance, but it is a sum of money above and beyond the principal balance of the mortgage you are refinancing and it has to be funded by somebody!