US NATO spending is excluded from official overseas base cost tallies.

Evidence

Aside from U.S. “rent” expenditures and “burden-sharing” receipts, the OCS also omits U.S. spending on the North Atlantic Treaty Organization (NATO). During fiscal year 2012, the Pentagon budget included 247.6 million for U.S. contributions to the NATO Security Investment Program, which went toward “the acquisition and construction of military facilities and installations (including international military headquarters) and for related expenses for the collective defense of the North Atlantic Treaty Area.” The Pentagon also paid 3 million for the U.S. military mission to NATO in Belgium, while the Army, Navy, and Air Force spent a combined 533.7 million to support NATO and to provide “miscellaneous support to other nations.” And the United States contributed 889 million of its own burden-sharing payments to support NATO member countries and other allies. — David Vine, Base Nation_ How U.S. Military Bases…, 630