I recently had a set of Rhino racks given to me by the dealer I bought the Dmax from, the type that clamp to the roof. They are Shit, they whistle and are very noisy compared my Thule racks. Where they hold onto the roof is shocking to say the least and there is no way I would put 10kg up there, let alone the max load.
Thule had released a fitkit for the Dmax but withdrew it due to problems, they have since redesigned the whole thing so it fits along the door jam and tucks under the top roof lining.
I would ask the guy what he wants for them, let him set the price and work from there, you might get lucky and pick them up[ cheaper than you thought.