The phrase "nice chunk of change" is an idiomatic expression that means a significant amount of money, usually in reference to receiving or earning it. Full definition
«But we made a really nice chunk of change.» (rismedia.com)
«That's a nice chunk of change, but it's not the complete picture.» (cnbc.com)
Organic chicken stock costs about $ 3 a quart, I think, so I figure not only did I re-purpose a significant part of my meal, I saved a nice chunk of change, too. (healthygreenkitchen.com)