I've had several Safelight repairs, and the insurance paid for the entire repair (and it was only $50 to the insurance co.- no deductible for the repair, but there would have been for a replacement of the entire windshield). The repairs are next to invisible, even if in your direct line of sight. There is a limit as to how much damage can be repaired, and Safelight will tell you if it can be done.
If the crack has spread to an edge of the windshield, I'm afraid you are done. Safelight uses a vacuum to draw the air out from between the laminates, and fills the voids with a clear resin (the resin has the same refractive index as the glass, that's why most of the damage becomes invisible). If the crack reaches the edge, you cannot make a good vacuum, that is why it is best to get it fixed EARLY.