The unit cost for each bomber is around $564 million in 2016 dollars, or about the same as five F-35A stealth fighters
There was a congressional research service report on the Air Force B-21 Long Range Strike Bomber in April 2016
The B-21 is intended to operate in both conventional and nuclear roles, with the capability of penetrating and surviving in advanced air defense environments. It will be capable of operation by an onboard crew or piloted remotely. It is projected to enter service in the mid-2020s, building to a fleet of 100 aircraft.
What Is Stealth?
“Stealthy” or “low-observable” aircraft are those designed to be difficult for an enemy to detect. This characteristic most often takes the form of reducing an aircraft’s radar signature through careful shaping of the airframe, special coatings, gap sealing, and other measures. Stealth also includes reducing the aircraft’s signature in other ways, as adversaries could try to detect engine heat, electromagnetic emissions from the aircraft’s radars or communications gear, and other signatures.
Minimizing these signatures is not without penalty. Shaping an aircraft for stealth leads in a different direction from shaping for speed. Shrouding engines and/or using smaller powerplants reduces performance; reducing electromagnetic signatures may introduce compromises in design and tactics. Stealthy coatings, access port designs, and seals may require higher maintenance time and cost than more conventional aircraft.
As the United States has gained experience with stealth and advanced its technologies from the F-117 through the B-2, F-22, and F-35, some of the operational and maintenance costs have been reduced. The B-21 will benefit from that knowledge, although some of the performance compromises inherent in designing for stealth cannot be avoided