When researching this myself in recent months, I found the Makita BO6040 to be the closest thing I know of to a RO150; last I looked it sold for around $600, the Rotex about $940. $600 is still a lot of money but that can be absorbed a little easier over a number of jobs it's assigned to do.
http://www.makita.com.au/products/po...der?Prodid=166
The CT36 was recommend to me to use when I was considering a Rotex; it was quoted at around $1100. It's absurd to pay this amount of money for a vacuum cleaner (for that is largely what it is) that is not really suitable for use outdoors. It has limited hose length like all others, it's not designed to drag over rough ground, you can't conveniently take it up a ladder or scaffolding typically when sanding weatherboards. The rotex works best WITH one. Kind of an absurd situation isn't it?. Fellow forumites have responded to me by saying get the rotex and get a cheap second-hand dusty to go with it. Probably good advice.
As far as going down the the other end of the scale, forget it! You will waste your money. Buy something
fit for purpose. Some professional powertool sales people have tried to steer me toward one particular model of Metabo, I forget which one. It did not have forced rotation, it sat quite high above the work surface therefore was not suitable for prolonged vertical work, and each of these sales people had pale hands, long fingernails and had never used one. There's a message in there somewhere.