THE official opening of the giant outdoor statue of Buddha at the Po Lin Monastery on Lantau tomorrow will cost $30 million, half as much as it took to design and cast the 23-metre tall statue. The money will pay the hotel bills of hundreds of guests invited to the 9 am ceremony, as well as preparing the site of the statue for the thousands of people expected to visit it on the day. The sum also includes the cost of building a small temple at the bottom of the steps leading to the statue. A monastery spokesman said: ''We are trying to improve the environment around the statue, including the road leading up to it and the prayer ground.'' But the monastery was unable to give a breakdown of the costs involved or where the money was coming from. The $60 million cost of the statue was paid for by donations from the faithful in Hong Kong and around the world, including $5 million raised by Buddhists in China.