Strengths and Limitations

Strengths of this study include the ability to compare buyer-driven behaviour in a common but meaningless adverse purchasing behaviour outcome in a cohort of over one million eBay buyers for whom postage and delivery cost is occasionally covered by the seller. Despite potential challenges with perceived value-for-money, use of tracked postage ensured that 62.4% of buyers purchasing from the control seller in 2021 dating from the beginning of the study chose at least 1 other item (added value item referred to in this study as aV1) and 22.3% of the control seller's buyers contacted the seller before delivery asking for additional bundled item offers.

The study is limited by the buyer motivation nature of the examination, although our large sample sizes and universal ascertainment of deliveries may reduce potential selection bias in our primary analysis.  For buyers with high-risk feedback or transactional complications, stalking of their social media was performed on a buyer-level basis by faculty socmedists in the Buyer Behaviour Clinic of the University. We acknowledge selection bias which informs the cancellation of a small number of transactions.

(Academic nonsense deeply pleases me...)