Shares in the company which operates the East Otago and Reefton gold projects fell from $A2 ($NZ2.47) on Tuesday to $A1.44 ($NZ1.78) on Wednesday before recovering to $A1.53 ($NZ1.89) yesterday.
The gold miner said on Monday the capital cost for the Didipio gold-copper project in the Philippines was now expected to cost more than double the original cost of $US155 million.
The revised price had soared to $US320 million ($NZ418.3 million), of which $US40 million had already been spent.
ABN Amro Craigs broker Peter McIntyre said when contacted that the 38% fall in share price on Wednesday showed how volatile the market was when it came to such announcements.
"The market was trying to decide what impact the increased costs will have on the profit for the coming year. It is not good news for the company."
While cost blow-outs were not unusual in the industry, OceanaGold was a small to mid-cap company and increased costs were not as easy to hide as they were for large miners like BHP and Rio Tinto.
OceanaGold was likely to keep the market fully informed on any further developments, Mr McIntyre said.
The company would be hoping the Didipio project would become a "cash cow" but the diversified country base had added more risk to the business.
