I don't know if this happens in other countries, but here curry powder comes in fairly small containers in supermarkets, so what I do is buy a larger plastic pack from an Asian grocery story when I am out of town.
I make garam masala from whole spices, but I buy "curry powder" for Jamaican and Japanese curries. I buy a paste for Thai (as the individual ingredients get too expensive, or I make too much and it goes to waste. The powder comes as bulk, and I get about two ounces at a time. It's not the cheapest, but it's more economical than the tins.
