A Space Force may only cost the Pentagon $550 million more per year, amounting to only a fraction of the estimate put forth by the U.S. Air Force, according to a defense budget analyst.

While the total cost for a Space Force could amount to as much as $21.5 billion annually, most of that money is already accounted for in the Defense Department’s budget for space personnel, operations, and procurement, according to Todd Harrison of the Center for Strategic and International Studies.

"Most of this is just a simple matter of reorganization and whether or not you think that’s worth it," Harrison told Defense One on Monday. "The added cost is a handful of F-35s or less than the audit. I don’t think cost actually should be that big of factor in their decision. I think a bigger factor is whether or not it’s needed."

Harrison analyzed the costs for small, medium, and large forces, pegging the cost of a Space Force between $300 million and $550 million per year in additional funds.

According to Defense One:

A lesser Space Corps kept within the Air Force comprised of about 27,300 uniformed military and civilians would cost about $11.3 billion annually, he said. A "Lite" Space Force — of about 35,800 military and civilians would cost about $13.4 billion annually. A "Heavy" Space Force of about 48,500 military and civilian workers would cost about $21.5 billion annually.

Depending on the option pursued by the Pentagon, Harrison estimates the force would cost taxpayers an additional $1.5 billion to $2.7 billion over five years.

Regardless of the force size chosen, he said 96 percent of the funding is not new, "it’s just transfers from other accounts that already exist in the services."

Harrison’s estimate is closer to the cost put forward by Deputy Defense Secretary Patrick Shanahan, who said last week the initial costs of a Space Force would likely be lower than $5 billion and definitely within the "single digit" billions of dollars over a five-year period.

Both estimates are far lower than the Air Force’s proposal, which estimated the force would cost nearly $13 billion in new funding over the first five years.