To my understanding, the total spending is around $18B, so the allegation that 50% of all spending is fraudulent requires quite the sniff test. Additionally, large multi-billion dollar fraud causes are usually associated with large organizations (like a hospital or insurance system) which is not the case here.

Could it be $9B+? Stick enough vague qualifying words around your presentation of the probable truth then yea, sure - at least $9B in spending could be fraudulent.