I don't have a dollar figure to quote you here, and I'm not going to invent one. What I can tell you is what drives the number on a door like the ones common in Glen Ellyn: whether you're replacing a full set of ten rollers or just the worn ones, whether the hinges and brackets need replacing alongside them, and whether old steel is being swapped to nylon as an upgrade versus matched like-for-like. A door with original 1972-era track that needs realignment on top of the roller swap runs longer on the clock than a straightforward swap on newer hardware. The only way to get an honest number is to have someone look at the specific door - sight-unseen estimates on hardware this old are usually wrong in one direction or the other.