Curb weight is simply the weight of a car with no passengers, cargo, or anyting other than the standard base model options.
Basically it's the weight of a base model car sitting on the dealership lot. Curb weight would be different if ANYTHING is added to the base model car such as a passenger, any cargo, or any upgrades aftermarket or otherwise.
The total of the prices of all of the baby shirts and sweaters that the store sold during the sale was $420.00. It's possible that 12 sweaters and 8 shirts are sold a bargen