With rockets re-usability labour is probably the most expensive as you need to assemble lots of custom parts into engines and triple check them. Materials are expensive but probably less so relative to engineer labour.

When rocket has flown and landed, you still need to go over all pipes, pumps, turbines... and check them before they can be reused. You are saving on materials but labour intensive checks still need to be done. With today's tech, you could add 100s-1000s of cheap sensors to automate some of that. There is point in rocket reusability but it's not so clear cut as with cars or planes.