Say I have €100 to put away for 40 years and can get a long term rate of 3% on deposit savings gross of tax.
If PRSI didn't apply and DIRT was 20% (as it was a few years ago), I'd have €258 after 40 years.
Applying a total of 45% PRSI and DIRT (current situation), I'd have €192 after 40 years.
In other words, the increased taxes on deposit interest of late have effectively knocked 25% off my ultimate proceeds, this is far worse than even a 0.6% levy over the same period.