DR. ARTHUR LAFFER -- he of the breaking curve that promises both simultaneous decrease in the tax rate and increase in tax receipts -- has at least one practicing disciple at Reagan transition headquarters: Verne Orr.

Mr. Orr, who was one of Gov. Reagan's California state finance directors, is the transition's deputy director for the administration and budget. He certainly does bring a fresh approach and a refreshing candor to his Washington duties.

Take the matter of the spending by the Reagan transition "team" for personnel and other expenses. Congress appropriated some $2 million for transition expenses, the same amount available to Jimmy Carter's "team" in 1976. That year, the notoriously free-spending Democrats somehow managed to return to the Treasury some 300,000 unspent dollars.

This year there will be no such refunds. The Reagan transition, the veritable C5A of political endeavor, has been hit by what some have called a cost overrun. Mr. Orr has already advised all who pay attention to things such as public appropriations that the Reagan transition will spend somewhere in the neighborhood of $2.5 million, which is a neighborhood 25 percent ritzier than the one appropriated by Congress.

But you will get no apologies from Mr. Orr, deputy director for administration and budgets. No, sir. Here is what he has had to say on the matter of budgets: "We think we're running substantially under what our budget was . . . we're going to come in at about $2.5 million." Mr. Orr hastened to explain that the $2.5 million figure was "not in our terms over budget; it's under budget."

After explaining that he had expected the transition to cost $3 million, Mr. Orr observed that while the figure spent may be "over and above the appropriation . . . we never made the slightest effort to work under an appropriation which had not been upgraded for four years."

Mr. Orr, who has already expressed his disappointment at being passed over for the Office of Management and Budget job ("I had my sights set high"), could be the answer to the coming administration's major challenge in trying to cut spending and taxes, to increase the defense budget and balance the budget. Mr. Orr has brought us the "Subjective Budget." Now that's something new.