Doris felt that Roger was spending too much money on services for the annual charity ball, so she leverages the philanthropic nature of the event to significantly drop the price on all the services that Roger purchases. The end result: $11,553 extra for the orphanage fund.
The power gets cut at Scrooge McDuck's venue, and he interprets it as great savings. To save even more money, he fires the planned act and becomes the performer. His guests are not impressed and leave the venue.