CURRAGH Mine spent almost $300 million so it could move another 2 million tonnes of coal each year - but already its bosses are talking about watching their wallets.
In a telephone hook-up following the full-year results from owner Wesfarmers, managing director Richard Goyder said Curragh's growth would allow it to move more coal for less, cushioning the low price of coal that was hurting miners.
But he said it would still "put some pressure" on the business, and certainly on other mines that were of a smaller scale.
"That is one area of the business in the short term that is a concern for us," he said.
"You'll find mining businesses really pushing down on costs as hard as they can because the high revenue isn't there."
Even as Curragh sold almost 25% more coal in the past 12 months - from about 7.9 million to 10 million in the period - new royalty costs, lower coal prices, flood repairs and the final stage of its expansion consumed most of those gains.
However, Mr Goyder said the company was already doing the ground work for another expansion of the site, clearly planning for a time when coal prices rebound.
"We want to see the mine operate at its new capacity and we want to bed that down," he said.
"But we continue to do some work on a further expansion."
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