I bought a gently used on on ebay the year before last (because I wanted to try one out without paying full price). I'll say this; if you can afford one, they're worth the investment so far as being a quality tool for the cockpit. They're comfortable with good sound delivery, enhance communication, and for such little pressure on the head, they work surprisingly well.
For less money, lightspeed headsets are good, and a lot more comfortable than a david-clark type.
I took that used set of Bose to the middle east with me. It sat in the heat and the dust and got bounced around. I put it on when outside doing engine runs with turbojet equipment...and I was pleasantly surprised that even standing in front of a jet engine, it still did just fine. (I figured it would have been okay for the cockpit, but not outside next to the engine doing runs...turns out that even though it doesn't clamp down over the head like a seat of ear muffs, it does unexpectedly well).
After about six months I was getting intermittant hissing and popping. When I ended up back in the US, I stopped by the Bose booth at Sun n Fun airshow. I mentioned to the folks in the booth my experinece with the headset. They told me the hissing and popping was probably a worn ear seal. True enough, where the seal rests against my jaw, if it's been any period of time since I last shaved, the stubble tears up the ear seal. They handed me a replacement pair at no charge, as well as a hat and some literature. The new ear seals took care of the problem.
Even in the heat and adverse conditions, the headset held up, and the batteries lasted a long time. I kept an extra set in my flight suit, but didn't need them. I haven't got around to trying it in the 747 yet (some tell me it creates impedence problems)...but probably will. For a good all around light airplane headset, the Bose X works great.
You might try ebay first...I got a heck of a deal.