Especially for a high level necro that would make the most use of this. It's more game changing than JBoots and everyone with JBoots knows their value.

Everything depends on how much you play the class and what level of gaming experience you wish to have. If you don't really play your necro, then you don't need one. If you wish to unlock the full capabilities of the class, the pre nerf CoS is a must have item and it's the 1st item you should get, followed by "The Unholy Trinity": manna robe, VP staff, beads/stalking probes.

If any of you would like further explanation on the capabilities, shoot me a /tell in game and I'll enlighten you.

Unchainedfury

Does it help you farm green wolves during statue and KTs?

Most of what I am going to say has probably been covered.

The price is increasing due to rarity increasing. The number of pre-nerf CoS's is always going down on Blue. People with them stop playing, people destroy them, drop them, etc. I sold one for like 4k back when they were still dropping. Then bought one again a year or two ago for 40k. Now it sounds like they have gone up again in price to 70k. At some point the price will level out, but it seems like that hasn't happened yet.

The biggest benefit to pre-nerf CoS is saving bag space. To many people (especially newer players), this may seem odd. I myself have 5/8 bags basically always full of stuff. Clickies, food, spell reagents, resistance gear, etc. If I had to lug around another bag or two of invis pots or rings, I basically wouldn't be able to pick up anything from mobs. As you level up and acquire more gear, bag space only becomes more valuable, and you can never increase it past a certain point. Necros will probably be carrying around a bag or two of stalking probes already, because most people can't afford beads. Beads are 10x more expensive than pre-nerf CoS lol.

You can do some fun things with pre-nerf CoS in terms of being able to stand up and instantly invis. This certainly saves time, and can allow you to get through dungeons a little easier. This is because you are not required to find a safe spot to cast invis every time you stand up. You still need to do that in dungeons where some mobs can see invis, but it helps with exploration in a lot of areas.

Charm breaking is also good. Pre-nerf CoS is superior to the Goblin Gazughi Ring because you don't need to target yourself, and the invisibility is not limited to animals.

Finally, CoS can be clicked from inventory, which is more convenient than Goblin Gazughi Ring or Ring of Stealthy Travel, which need to be equipped.

That being said, I wouldn't rate pre-nerf CoS as a must have for all Necromancers/Shadowknights. If you are just casually playing the game, you can probably fit a bag of invis rings into your build. If 70k is a huge sum of money for you, prioritize spells and Staff of the Dreaded Gaze. Then you can buy a Ring of Stealthy Travel and Goblin Gazughi Ring to save bag space and have charm breaking + fast invis. Not instant, but the 2 second cast is still pretty good. Just re-sell them for money towards the pre-nerf CoS if you get the desire for one later.

invisbility is increasingly useless as you level up a necro, especially since you will often be cavorting around the undead which naturally see through invis. further, with non memory wiping mobs, the idea of standing up and insta invising is something fun you did at level sub 30 and have fond memories of but then never bothered to try again because it simply no longer works reliably.

TLDR: just buy a gaz ring.

nerfed CoShadows still allows from inventory cast. right?

Yes and you can still get rings for instant

Invis still works in plenty of places at high levels. Howling Stones is a good example, you can get around with FD and using Invis + lulls for undead.

What do you mean it "works" in howling stones? Howling stones is full of mixed groups of live/undead enemies, half of which will automatically see you, aggro, then bring their "blind" friends with for the /assist and /teabag.

It works quite well, I get around with it all the time in Howling Stones on my Shadowknight. You lull the undead and invis past the living mobs. Pretty simple. Having an instant cast Invis clickie certainly helps with this.