How many miles on your Prix? How are the roads in your area?

These two things can factor into the suspension greatly. Another thing is to pull the wheels and look at the struts. If they have oily residue on them, they leaked and are shot. That's one 100% way to know if they are shot. They can also get bad w/o leaking. But if it's as bad as you say.. it kinda sounds like they will probably have leaked.