sentence1: So, bidding should be leisurely when bidders have little to learn from each other (say, when they're bidding on a new computer that's been widely reviewed) and intense when some bidders are far more expert than others (say, when they're bidding on a heart defibrillator for home use).
sentence2: When bidders don't have much to teach one another, there's no need for bidding to be done intensely.