Certainly, and much more. I personally think they are worth at least 5 – 10 $. But it is a fact I do not feel obliged to have to justify the price of 0.99$ or 2.99$ whatever.
John Locke says that he does not need to prove that his books are good because he is offering them for only 0.99$. So now all those offering books for 9.99$ have to prove that their books are 10 times better.
So, stop wondering if your books are good enough and direct your attention to the right way of promoting them instead. This means you must attract your target group. They will assess whether your books really are worth the price you are selling them at.