Drinks in Vegas are pricey! One of my favorite places to sit, have a drink, and people watch is the Parasol Down bar at the Wynn. I've never actually sat outside to see the water show, but sitting inside you can watch all the people coming downstairs to dinner at one of the two restaurants there, or those who just wander down the curved escalator and back up.
You should expect to pay between 10-15$ for drinks on the Vegas strip. And that's just the average. They can definitely be far more. That being said, I love the Peppermill. They have some great specialty drinks and a cool atmosphere. Other than that, all the bars are pretty similar to me, but I'm a local, so who knows.