While the past perfect is used for the first of two connected past actions, we don't always use it in a consistent manner. We often skip it and often use it for emphasis.
Here, the pleading did start earlier that the leaving and returning, but if the past perfect were used, then it would imply that the pleading had stopped before the return trips were made, which is not the case. So, she did plead before she left, but she also pleaded later- that action runs across the trips. The past perfect serves to emphasise the number of trips required before the important action of reducing the price occurred.