I mean... I'm going to assume you're an FO and use an arbitrary $250/hr pay rate for a 4-day trip. That 4-day @21 hours x $250/hr = $5,250. They could have used you as a reserve for zero extra dollars (you're getting your guarantee anyway), and instead choose to pay $5,250 x 3 for the 23M7 and IA = $15,750. That's probably a third of the cost to hire another scheduler. All because they didn't have the staffing to properly notify you for the trip properly.

Unbelievable indeed, yet happening every day.