You brought your car in to the tire shop and were quoted a basic tire alignment price. Some time later, the salesperson came to you and told you they would need to charge you more to be able to complete the alignment. You’re told something about unforeseen difficulties is the reason. Most cars have adjustment built-in for alignment angles. However, sometimes your alignment will be farther out than the adjustments will correct for. So they’ll need to install a shim or an eccentric adjuster. If you live in an area that gets lots of snow, slush, ice and salt, it may have corroded the adjusting sleeves for toe settings. This means the technician will have to take extra time and maybe use a torch to be able to make the required adjustments. These are just a few of the possible reasons why you may be asked to spend more than the original estimate for an alignment.
For more info, see Is Tire Alignment Worth the Cost