Ann: Bulletin Delivers Robust Feasibility Study , page-8

re: Ann: Bulletin Delivers Robust Feasibility... question for an expert

re:

"The estimated pre-production cost for the mine development of the two pits at Nicolson’s is $8.9 million. However, drilling has commenced at Wagtail and Rowdies with the aim of upgrading the Inferred Resource to the Indicated category. Should this prove successful, open pit development will commence on these deposits, which is expected to reduce the pre-production mine development cost requirement to $7.2 million."

how does mining 3 more pits 500m-1km to away reduce the total pre-production development cost?