This is a good point that shows the weakness in a lot of these comparing military budgets. Imagine an example where one country spends $1000 per soldier and another spends $100k per soldier. IF they both field 100 soldiers. One budget is 100x the other, but by PPP they are equal.

A practical example is health care. US Gov gives free healthcare to service members. This is in the military budget. A different gov which already gives free health care to everyone, would have this in a different budget even if its effectively still supporting the military for each service member.

US Soldiers/Airmen/Sailors/Marines are incredibly expensive each.