variations in price of Black Tea and Half & Half at starbucks

this drink does not exist so im convinced the person taking my order just makes up a price
  1. $2.25
    2/23/17 - Starbucks truck on Busch
  2. $4.35
    2/24/17 - Livi Starbucks
  3. $4.23
    2/25/17 - Starbucks at the Yard