Repairing or replacing your concrete driveway
If the cracks are narrow and the slab still sits level and drains, a repair or cutting out one bad section is often enough, and I'll tell you so. When the driveway has sunk, broken into many pieces or tips water back toward the garage, the ground under it has usually given way. Patching the top then leaves the new concrete on the same soft base, so that's when I'd recommend tearing out and starting over.
What shapes the cost of a concrete driveway
Beyond size and tear-out, the cost depends on how much digging and grading the site needs to drain properly, how thick the slab is, whether it's reinforced, and how easy it is to get equipment in. Curves and tight spots add labor. When the budget is tight, people are tempted to save on the base because nobody sees it on day one. I'd sooner trim the size than skimp there, because the base is what keeps the slab flat.