There is a few variables that can help explain that high budget.

Our military vehicles are maintenance heavy. I’d almost rather take on the extra knee and back pain by being with a light unit than deal with vehicle maintenance. From mechanic to just the regular soldier, all are on hand to fix shitty trucks.

The equipment you see being used by the military has to be made in the US. From the uniforms we wear to the ships we sail around in, and everything in between, has to be made in the US. This is going to drive the cost up, while yes the quality will be better than something made in china, it also comes at a higher cost because you have to pay those workers a higher wage.

Research and development is costly. Private gun ownership kinda takes a bit of this burden for our small arms I would argue though. Magazines are an extreme pain to perfect. Optics can have a number of issues. What materials make for the best hand guard, foregrip, stock, sling, so on and so forth, the civilian market really helps to figure this shit out. But the civilian market isn’t going to figure out the best steal to use on our tanks, stealth technology, and so much more.

The medical system and big pharma have their claws in the military health system as well. HIV medications? Still cost the military the same as it would a civilian without insurance. Thousands of dollars for just one month. Same with insulin. Same with epipens. It’s cheaper to do x-rays or MRIs, because you already have the radiologist in the army as well (ideally you would at least). They get paid the same regardless of how many x-rays they look at.

Training is expensive. Ammo is expensive. Fuel is expensive. The required maintenance you’ll need to do on those vehicles you used in training is expensive. And even still, some units will only zero and qualify their rifles once or twice a year. It now takes 75 rounds for a soldier to zero their rifle and complete a qualification range. 35 to zero, 40 to qualify. Multiple that by half a million, that’s how much it costs for the entire army to go and qualify on the M4 one time a year.

Waste, fraud, and abuse are a real thing in the military. But people do forget just how expensive so much of this shit is by itself.