This is not just for Obama, but any POTUS, I think there should be some kind of "budget" for how much taxpayers should pay for vacation expenses. They may pay for their own rooms, and for their first class tickets, but that is a drop in the bucket v. the total costs.
There should be a budget, and when it's used up, they go to Camp David for a break. POTUS and FLOTUS both have enough personal assistants to keep track of getting the budget to last over the course of each year or term.
$16 million just for Flight times to Honolulu & Africa in one year. Can you even begin to imagine what the total cost was? But there's still no $ for WH tours because the Secret Service is spending too much?
And when it comes to attending fundraisers, there should be some adjustment to the costs to be paid by the individual political parties. It is not a fair arrangement in election years especially. Again, both parties should have to play by the same rules.