I've noticed on a few products at Amazon, it will be cheap while one of the supermarkets, say Woolworths, has it on special. Then the next week, when the Woolworths special ends, it will jump back up in price.
Is this a strategy that Amazon are employing, is it something that only certain brands are doing?
Amazon would have bots that check prices of groceries, electronics, video games etc. online, they will then adjust their prices (in a certain allowable range) to ensure they have fairly competitive pricing.