The company I doubt "allows" you to buy business class. It wants you to fly business class so that you're in a better shape to work after the flight. Flying in coach will leave you in a reduced capacity to work at your destination. In case of IRROPS moving your to coach, your capacity to work is reduced (in the company's mind) although they likely aren't going to shortchange your pay for something out of your control that they wanted you to do. The flight is not part of your compensation, it is part of your company's providing for your dispensation of your job duties. The impetus for the flight is the company, not you. And of course, they are paying. So, ethically, they deserve the money back.