There is a cheaper way. They make adapters that go over the studs on your 4-bolt hub and have 5 studs coming out of it. It is still basically a 4-bolt system but allows you to select from a wider variety of wheels.
Like these: Adapters
Now if you want the true deal, then you are going to have to change out your suspension compontents. How much you have to change out will depend on the vehicle.