Also, many companies / governments have different procedure for stuff over $X, but $(X - 1) might be easier. Doubt anyone has a break at $1599 vs $1600 though.
It is often easier to order a $4,999 item than a $5,000 item.
I know the concept of price ending, but my point is that 1. WWDC sells out anyway, and 2. It's mainly companies paying their developers to go here.
Your second point might be technically accurate, but there's a very large contingent of indie developers, like myself, with 1-5 employees that shoulder all the cost ourselves.