This is old problem in cRPG, but after last patch weight was increased once more.
Let's talk about Real Life weight.
Weight of an arrow for longbow (length of an arrow 85-95cm) = 50 gram
Weight of 20 arrows IRL = 1 kg
Weight of an leather quiver (quiver capacity - 20 arrows) = 455 gram
Therefore RL quiver with 20 arrows weigh 1,5 kg.
I wonder, why ingame quiver with 20 arrows weigh 4 kg?