An insight is a non-obvious truth about the audience that explains their behaviour and opens a door for the brand to be relevant.
An observation says what people do. An insight says why — and the "why" is uncomfortable or surprising enough that it was not already obvious to everyone in the room.
A practical test: if the opposite of your insight is absurd, it is not an insight, it is a fact. "People want good value" is a fact. "People buy the cheap option and then quietly hide the receipt" is closer to an insight.