Refer flap15's comments:
1. For carbon brakes, each application is a wear cycle. So, multiple brake applications result in more wear/cost.
2. Ironically, a low Autobrake setting can result in multiple applications (more cost), wheras a higher Autobrake setting may result in fewer brake applications (less wear on carbon brakes).
This is why Boeing recommends a higher Autobrake setting in normal operations rather than a minimum setting.