When pressing on the throttle it doesn't jerk, but then then crusing/no change in speed the car starts to jerk, the guy at discount autoparts said it would be around $100, Does this sound correct?

EGR should not do that. Its there to help emissions and milage... Herky jerky if fluxuating fuel pressure, bad coil(bad spark) jumping spark arc's... ect ect.

YES . The EGR will cause the car to jerk at cruising speeds . Fact is the EGR is used for emmisions it draws exhaust gases back through the engine via. intake vacuum.
When the EGR or the EGR vacuum solonoid go bad the EGR draws too much vacuum making the engine run too lean . Its like having a bad vacuum leak. It is most noticable at cruising speeds especially if you have an automatic transmission because of the locking torque converter ,because your engine is locked into the rest of the drivetrain.
Not saying that the EGR is the cause of the problems with your car , but it is a very good possibility.
I just replaced my EGR vacuum solenoid because of the very same problems and now the engine runs great.
Hope this helps.