Best Way to reach 500 hp ,, Cheap !

these kinda questions make me LOL.

You need to clarify one issue....do you want 500 at the rear wheels or 500 at the crank?

There is a huge difference.

In the end....Boost is the most efficient power adder....and the most efficient method of forced induction is turbocharging....it practically doubles the engines breathing ability....and all engines are nothing more than air compressors with internal combustion.

It takes a pretty radical engine combo to put 500 to the rear wheels if you want to stay naturally aspirated....and IMO it would hardly be any kind of "streetable".