For clarification . . . your talking about repair costs for a LEXUS not Toyota correct?
Trying to figure out how you needed to replace all four shocks and require substantial work to the KDSS. Did you run the Baja, have a million miles on the truck or loan it to your wife?
Yes, this qoute is from a Lexus Dealership, but I don't think the cost from a Toyota Delearship would be too far of, if I could find one that has the equipment, and would do it.
We bought the GX470 about a year ago with 81k miles on it. It now has 90k miles on it, but has had the suspension issue from the beginning. It may even be why the PO got rid of it. From what I can tell it has never been off-roaded or abused. It has just been on pavement duty like most lexuses. And like most lexuses, it has had all maintenance done at a the lexus dealership.
The KDSS rear actuator leak is just due to normal use and age, and is the source of the suspension clunk. The shocks do have some seepage, but I don't think it is bad enough to justify replacing they yet. If it came to it though, I could replace them with a set of Bilstein 5100s for the cost of just 1 rear Lexus/Toyota AVS Shock....
The real problem is the work the KDSS System uses, as you need to have a Lexus or Toyota dealer to do the work, unless you want to buy a $500 tool, and try and do it yourself.
The Rear Actuator is about $500 for the Part, and as JerseyMike showed, the labor for bleeding the system is $500 (including the $50 in fluid). I would imagine the labor for installing the actuator would be in the neighborhood of $500. And since the rear actuator lasted only 80k miles, who knows how long the front actuator will last, and when that goes, it will be another $1500 to fix.
The huge KDSS Swaybars do make the GX handle almost sports car like in the twisty backroads, and is very nice, however at this point, I wish I had gotten a non KDSS GX470.