Myth or facts?

So today I asked one of my gyani uncle abt the 13-day shraad or last rites ritual performed in the Hindu religion after death

He said it is done to purify the soul; once the soul is purified, it will get moksha or freedom from this cruel world.

Is it true? like spending lakhs even after death just to purify the soul, or is it a way for pandits to earn money through it?? Most of the rituals are useless, baseless