The left digit bias

the idea that $7.99 seems cheaper than $8, even though $8 is only negligibly different than $8.01

is about more than just pricing

patients who were slightly over the age of 40 were almost 10% more likely to be tested for a heart attack than those just under 40. The difference shows up as a discontinuity, a jump up in the probability of being tested as patients cross their 40th birthday

The first digit in a number might matter more than all the rest

A car with 39,990 miles on the odometer sells for more than a car with 40,005 miles