Is it at all worth paying into a third pillar?

Balances in 3a accounts barely post any growth because interest rates are practically zero, and therefore there is no compound interest effect. This is unlikely to change in the near future. That is why a cost-effective 3a solution with securities is a better option. While they involve more risk over the short term, it is very likely that over the long term they will generate far higher returns than a 3a account.