Ba does not produce the same secondary legal result in every sentence. Its foundational meaning is attachment, but the connected item may be a price, a report or an object of wiping.
Consideration: the attachment links an article and its price.
Report: the attachment asks whether a statement corresponds to the event it describes.
Wiping: the attachment relates the act of wiping to the head.
For reliable interpretation, first identify the main verb and the noun governed by ba, then determine the legal relation between them.