If you read the threads regarding how much people pay for their prius
You'll discover that most people have paid MRSP, although there are a few others who have saved up to $1000.
It all depends on your bargaining skills, your patience, and luck.
I assume you havent bought your car yet, so I would suggest you call around different dealers in your area and get the best price. I would have them bid for your business. At least that's what i did.
I saved $1700CND off mine, Plus got free hood deflector and side window visors, plus i paid cash
It never hurts to wait, doing business to buy a car should NEVER be hasty. I took my time and i ended up with mine after 7 months. At first, I always wanted a prius but bought an HCHII, but the dealer coudnt deliver on time so I ended up with a Prius. Taking time can also give you the opportunity to save more money; who knows, if it takes long it may give you an opportunity to save up even more for a better and more luxurious package or you may even change your mind and end up with an HCHII 06.
but it's up to you, it's your money.
good luck,
gj