Given the current WR (€ 0.000000313970828418996 / each BNK) and the current price of 1 BNK (€ 0.00162932) we have an interest of ca. 1%
which is okay given the negative interest rates nowadays. Of course in the past things have been better as we had the cards and IBAN running:

"This revenue share is equal to 0.00116868993 EUR per 1 BNK of annualized return. This is equal to a 11.7% annualized return given the pre-ICO price of 0.01 EUR, 6.7% annualized return given the initial ICO price of 0.017 EUR and 6.3% given the current ICO price of 0.018 EUR." - 19th WR report (https://blog.bankera.com/2018/01/08/the-19th-week-net-transactional-revenue-share-has-been-paid/)

Now imagine those services (cards & IBAN) to come back and the new services (exchange & loans). In combination with the current low price of BNK that will become an attractive interest.