What expensive tool is absolutely worth the price?

I have one that we were just discussing this past weekend: Griot's synthetic clay bar. For like $25, you get a piece some kind of rubber bound to a foam handle.

But it's totally magic for pulling junk out of the paint. You can hear, see and feel the difference.  

In reply to David S. Wallens :

I've heard before that clay bars are definitely worth it if you really keep your paint clean. Next time I'm buying car care products, I'm going to go all out.

The Eastwood brake line flaring tool.  It turns a sad job into an easy one. 

Good torque wrench. You're using one for a reason, you can't afford a bad one. 

A lift.  All sorts of things are easier when I can put the car where I want it.  I even use the lift for interior work - it's much easier to get under the dash when you can stand next to the car and work at eye-level.  $1,800 well-spent.

Pretty much any specialty tool that works correctly when needed. 
 

i was majorly impressed with following

quickjack

brake flare tool

bearing removers/presses

hub flange tool

Im sure there is plenty more, but just having the exact right tool for the job that makes it quick and easy vs having to just scratch, hammer, bang and inevitably getting pissed and breaking or damaging what you are working on. 

Power Probe.

Incredibly hand for electrical diagnostic. 

TIG welder, lathe, and a mill, and you can make or fix anything.

David S. Wallens said:

I have one that we were just discussing this past weekend: Griot's synthetic clay bar. For like $25, you get a piece some kind of rubber bound to a foam handle.

Jerk, now I have to have that!

A nice, high-quality multimeter.

I got a Fluke as a gift a few years ago and I use it way, way more than I ever would have thought.