I appreciate how much work you put into backing up your argument, but there are several flaws here.
-Goggles of Darkvision are a ridiculously overpriced item. Seriously, you can (by the suggested DMG table for item creation) use a spell from spell compendium to get a limitless use activated darkvision much cheaper. And if using MIC guidelines for what things are "really" worth, the price drops more. Also, the Dark template's darkvision doesn't stack with racial darkvision far as I know, and I'd hope any sneaky character would already have such a key ability before he could drop 10-20k on one item.
1) DMG table for item creation has a first step of "compare to existing items", not "look at the table". Plus, a Use Activated item of True Strike is the poster-child for why those tables aren't so grand (2,000 gp for +20 to all attacks, 4,000 gp if unslotted).
2) The Goggles of night don't stack with darkvision, either. I'm comparing what it does for a human, as a default, as the template the collar grants gives a particular set of stuff, and someone optimizing things will avoid overlapping abilities.
-Lowlight vision: A first level spell, and IME hardly a necessary thing to have.
Also not included in my cost calculations. And no, it's not necessary, but it's one of the things that's granted, so it's something I check when contemplating balance of the item in question relative to core items.
- You're saying the collar's good cause it's giving all these things in one slot. MIC says slots aren't as important, as long as you're tacking on common effects, including those skill bonuses. In fact, it could be argued that almost no character will ever need everything from that grab bag, so it should be cheaper bundled together.
A stealthy character will make fairly common use of basically everything except the cold resistance, or stuff they have already. And the cold resistance comes up if your DM is fond of direct-damage effects. Hence I include it.
I think the minute/day version may be ok, and the unlimited use should probably be worth +50% or even +100% the current value, but that's a far cry from the numbers other people are tossing out.
Do note, with the items I listed, you're looking at about +50% for the no-duration-cap variant. Mind you, that doesn't cover either the Hide in Plain Sight or the Low-light vision, and uses lower skill points. Evasion, a 2nd level class feature, can be purchased as a ring for 25,000 gp. A Ranger's Hide in Plain sight is a 17th level ability, while a Shadowdancer gets it at 1st level... but the Shadowdancer requires a minimum of 7 character levels prior, so it's effectively an 8th level ability (comparing to Core, at least). If you follow the "standard" progression (level ^2 * some constant) for most items, using a 2nd level ability as a base (resulting in a "constant" cost of 25,000 gp /(2*2) = 6,250 gp), you get a value of Hide in Plain Sight of 400,000 gp. If you treat Hide in Plain Sight as being approximately equal in use to Evasion, then you're looking at that aspect alone being worth 25,000 gp - which is, in and of itself, more expensive than the uncapped collar.
Now, granted, there's a lot of internally imbalanced things in Core (Fighter-20 has significant difficulty keeping up with a Wizard-20 in terms of in-game usefulness, for instance), but balance is also a relative term. Relative to Core items, the no-cap version of that collar is significantly underpriced for what it does. By a lot.
I think the issue partly depends on whether or not your group uses LA buyoff from UA. if so, that +1 LA is effectively only worth 300 xp, and it starts to look not so bad. And it's hardly the worst +1 LA template. Just be thankful it gives no stat bonuses *looks angrily at that stupid Lolth one that gives str and con +6*
... you missed a 0. 3,000 xp for a +1 LA buyoff.
Of course, the LA buyoff rules are badly worded. You're an Aasimar Sorcerer-2, who just hit enough XP to become an Aasimar Sorcerer-3 (6,000 xp), so you spend 3,000 xp to remove the level adjustment, leaving you at 3,000 xp... which, with the +0 LA race that you now are, is still enough to make you a Sorcerer-3 - so you level up anyway - at no noticeable cost, even in the short-term.