[RallyDRock]

cams are like $400 + install
the install is difficult, engine must be unbolted and jacked up, front and rear (passenger/driver) side covers of engine must be taken off. with the new springs the cams will try and move when doing the timing. not something i would attempt in my driveway.
the springs just close the valves faster to avoid what is called valve float. no performance gains from just a spring change.
cam gears will move the power up or down in the rev range. so you may get more power but youll need to keep the revs above 3000 to see any of it.
unfortunately it will cost more than 600.

maybe a Nitrous express kit designed specifically for the PT or keep saving for the turbo?