I just think that the AR-15 is a simple tool, easy to use, and comes in many shapes and sizes.
You don't have to be a mechanic or a carpenter to know how to use an adjustable wrench or a hammer, I view my AR-15 like that.
I take it to work with me on range days, I use it for home defense, I use them for competitions, I use them for fun.
I don't consider a $1000 gun very expensive with today's list prices. Even still in reality, you can own an AR for much much cheaper than that.
You can spend 5x that amount on a nice precision bolt rifle setup, the scope alone if done properly will be worth more than my BCM carbine.
These days with work and what not, I hunt less and shoot more often, so bolt action rifles don't really cut it for me very long. Sure I have precision rifles, as well as some nice .22's to shoot tomatoes off the fence post with.
Really in terms of the grand picture, the AR-15 is an aforable, work mans tool. It might be more money than a WASR-10 or Remington 770 or the new Ruger American rifle... but honestly I don't buy that economy grade garbage anyway. Why can I make that statement? Because I see them coming back to our gunsmith quite regularly with problems.