Quarter panel replacement cost

The issue is the not seen parts, outer inner fender wells, trunk drop offs, rocker panels, you do have to have something to attach the new 1/4 panels.
Installing a new full 1/4 also involves removing most of the interior, headliner and glass.
It is time consuming, and a shop does not work for free.
Do as much as you can before you take it there, the bill will be less.