From my experience, most promotions are a salary band change. The company is willing to pay you more because: 1. They believe you will be able get a 'senior'

From my experience, most promotions are a salary band change. The company is willing to pay you more because: 1. They believe you will be able get a 'senior' band offer at a competing employer. 2. They believe that either you are worth the senior band pay or that you leaving will cost them more than the senior band pay.