Have to agree somewhat on the factory prices, I had an 07 GT 500 Mustang that had aftermarket springs, it literally was sitting on the frame bumpers. So went to local Ford dealer to order new springs, they said I had to have the Vin number of car!? I had just looked at a King of the Road mustang in the showroom so I used that vin, thinking they would be expensive. Turns out each spring (4) were $31 each. Surprise Surprise, sometimes there is a deal.
They did sit lower than stock but well off the bumpers.
Who knows what the prior own might have done. I have put many aftermarket lowering springs in many cars over the years and none of them put the car on the bump stop. Someone heating coils with a torch to get it lower though....
