i am not a teacher but still i can tell you what my interpretation is ....
when you buy something spending your hard earned money you try to utilise that thing to its max.
but when you get it without doing so much of hard work you dont really concentrate on that much. you take it lightly
here it says if you spend your hard earned money and purchase a book of php ,sql ,apache to create a website you read it thoroughly . But what would be the case if you would have got this book without spending your own hard earned money ... what if you would have got the book on your desk one day .that has been given to you by your parents or friends, would you show same amount of interest in reading that .
hope this might help you .
Student or Learner