I don't think your first dash is correct. It looks like they just integrate the curve in figure 4, multiplied by a 5% discount. This includes both tuition cost and missed work during college. Also, it's not really fair to represent this as a difference in lifetime income because of the discount rate: the college attendee makes significantly more than $100k more over their life, but the gains accrue later in life while the cost accrues earlier, so the discount rate makes the benefit smaller.