Minding the Gap in Sizing Up Sale Prices notes that consumers act as if low digits are farther apart than higher ones:
Students who saw ads showing a $233 skate marked down to $222 thought they were getting a larger discount than did students who saw a $199 skate marked down to $188, even though the opposite was true. The first group of students also rated themselves about 20 percent more likely to buy the skates than did the others.