Around here the trailer rockhaulers goes for 25 to 45 a rig,some have alumin tanks,rims and trailers some have polished tanks,rims and trailers some have just painted tanks, rims and trailers and these three can be cleaned in three different ways of each other.
Other things like water "we supply most not all" so you see they are alot of things that could bring the price up or down,,,main thing is to make a little money while washing.