'Stuff' is a smaller part of our economy than you might think. Software, Entertainment, Healthcare, Lawyers, Land, Prestige, etc.
Even then raw materials don't show up by magic. So, automation might get rid of low end restaurants, factory's etc but it's going to take high end AI to really kill 'the economy' as we think of it.
I think raw materials are actually going to be easier to automate. Australian mines already have self-driving trucks and US farmers have been at the forefront of UAV use.
Mines are a factory that use raw materials they don't make them. Consider some Ore in ground is raw martial gold is the end product. So, as long as people still value land gold is not going to be free.
Even then raw materials don't show up by magic. So, automation might get rid of low end restaurants, factory's etc but it's going to take high end AI to really kill 'the economy' as we think of it.