President Barack Obama and daughters Malia and Sasha left their vacation in Hawaii on Saturday, but left First Lady Michelle Obama behind on the islands, according to news agency reports. The president reportedly let his wife stay on in Hawaii with friends as a “birthday present.” Michelle Obama will turn 50 years old on Jan. 17.

It is a birthday present whose costs, in separate travel and security expenses, are likely to be borne, in part, by taxpayers. On a previous occasion, when Mrs. Obama left for a Hawaii vacation in advance of her husband, the additional cost to the Treasury was estimated to be at least $63,000, and potentially upwards of $100,000.

Mrs. Obama’s vacations have often been a source of controversy, beginning with a lavish holiday with friends in Spain’s Costa del Sol in 2010, and continuing with high-end sojourns in the Bahamas, Martha’s Vineyard and the Maine coast–the latter after urging Americans to vacation in the oil spill-stricken Gulf of Mexico.