Volunteer troops usually are contrasted to conscripts not to professionals. The United States for example fields an all volunteer professional military ever since the end of the Vietnam war. Unpaid troops are usually militias, and they can be contrasted to professional troops. That said militias often provide stipends or some form of compensation.

well, it's not incoherent to give a volunteer supplies, or even a basic stipend to cover supplies... If the 200,000 she mentioned was rubles, that's not even $2,200, that's not a soldier's pay, that's a small stipend—especially if they don't give you a uniform or even fucking feed you.