Would you face this problem that need you add payment if the costs is not enough for the bicycle samples.Yes.must have..But please understand them.Some time the final price depends on the complexity of the process,sometimes,They will take more time and energy for samples.Especially,the samples need to be developed firstly.The costs is big,and no profits. So if they tell you why you need to pay additional price,know the details and think about that. Welcome you to discuss with us.