Reading Prizes

My boys joined the summer reading club at our local library. This is the last week to hand in their reading charts. There are five charts total -- each with five hours of reading. They are given a prize as they complete each chart.
Today I read to them for about two hours because they really wanted to finish the chart they were working on. Now it is almost 11pm and my seven year old son says he will not sleep tonight because he wants to finish the new chart he just got today. He has no concept of how long five hours of reading is.
My six year old was falling asleep on his bed, but when I went in to check on him, he opened his eyes and asked me to read to him. Although he could barely keep his eyes open while he asked. I told him I would read to him tomorrow.
Such motivation. For what? A notebook! I will probably read to them for hours tomorrow so that they can get a notebook! I could go to the Dollar Store. I could go to Walmart and get a notebook for five cents with all the back to school sales. The last prize was a book, which has been, in my mind, the most valuable prize. But maybe it's not the prize that motivates, but that they really want to finish. They want to complete the goal -- to color in all the little pictures on the page. I bet if I asked them they wouldn't even know what prize they were getting.
But the thing I am wondering is -- Where is my prize? This is a lot of work!
On the other hand, I have enjoyed the time we've spent together. I really think reading is important for a child. Also, some of the books have been interesting and educational. I should sleep -- I have a long day of reading tomorrow.