You can earn good money if you don’t mind dirtying your hands.
Another version of this proverb is Muck and money go together; ‘bras ‘ is a slang word for money. We can appreciate the point of these sayings when we find ourselves in a great industrial area, with its factories and foundries, its smoky atmosphere, its coal mines, its ironstone mines, its clay mines, its slag-heaps.
In one of its sense ‘muck’ is the material removed in the process of mining. It has to be separated from the ores, and its presence in great pyramids shows that much valuable stuff has been extracted as well.
Both sayings can apply also to a craftsman – a potter, perhaps – who has not the time to clear up the mess behind him because he is too busy turning out marketable products.