If my math is correct, and it almost certainly isn't, if you had 100kEUR in savings, you would be taxed on "fictitious" returns on 42k. The fictitious rate of return they use is 1.44%, which brings your fictitious returns to 600EUR. You then owe income taxes on that return, which is 200EUR.

So your wealth tax on 100k is 0.2% or so...

Again, my math might have missed a zero somewhere.