 Costco says the 8% price increase will take effect September 1st. The price of the retailer's premium membership will rise to $130 from $120 now. This move will affect about 52 million memberships. Investors and analysts have long waited for Costco to raise its membership price. Costco has typically increased fees every five years or so, prompting analysts in recent quarters to ask about the company's thinking on the timing.