Recent stamps can be purchased from the post office, and the cost is not great. But for middle-aged stamps (ones the post office discontinues after six months or a year), classical stamps which are widely recognized to be of great value, or foreign stamps, one must purchase them from dealers, or join stamp buying cooperatives to bid on them, so naturally the cost is much higher.
近期票可向郵局購買，花費不高；但發行半年或一年後郵局窗口不再出售的中期票、歷史久遠有公認價值的古典票，及外國郵票，則必須向郵商購買，或參加拍賣會競標，花費自然高得多。