there isn't a rate for the air path per say, I have used mine on a couple losses, mainly because I was maxed out and all my equipment was out already. a 1hp axial pays like $35 something a day. I would just hit that for the air path.
charge the 35 a day it shouldnt be questioned, i use the airpaths when i conbine with heat it brings that heat down and across the floor way better than an axial on a stand does imo.