3d6 said:
A minor problem, to be sure, but I would still prefer that errata not introduce new problems into the rules.
And not really a problem at all. The cost for a cape of the mountebank is actually based on the formula for a command word activated item:
Spell Level * Caster Level * 1,800 gp = 4 * 9 * 1,800gp = 64,800 gp
It's useable once per day, which grants a price reduction of 80%, bringing the price to 12,960.
Now, the actual cape has a market price of 10,080, which is an approximately 23% reduction, likely due to "When he disappears, he leaves behind a cloud of smoke, appearing in a similar fashion at his destination," a limitation which is not present in the base spell.
So, if you want a CL 15 cape?
Spell Level * Caster Level * 1,800 gp = 4 * 9 * 1,800gp = 108,000 gp
Once per day: 21,600 gp
Unusual Limitation: 16,800gp
dcollins's usual counter example is stat-enhancing items, since their benefit is entirely independent of the item's caster level. The rules do not provide any method for pricing Gloves of Strength +2 at CL 5 vs. CL 20, therefore, he argues, you cannot arbitrarily up the CL.
I think the best rebuttal is to bring up the second half of my first sentence: "their benefit is entirely independent of the item's caster level."
If increasing an item's caster level has no appreciable benefits the majority of the time, then it should not carry a commensurate cost increase.
What are the benefits the gloves gain at CL 20 vs. CL 5?
- Better resistance to targeted dispel-type magics
- Better saving throws if unattended
As regards #1, I have never, in all the years I've spent playing 3E, seen a dispel magic targeted at an item. Anecdotal evidence is, at best, a poor way of rebutting points, however, but it's all I have, so I'll go with it.

I'll also point out that the duration of a targeted dispel - 1d4 rounds - is small enough that, in many cases, it likely won't matter.
As regards #2, it means your items have a better chance of not going kaput after you die and your party wizard fireballs your body to get the guys that killed you. This is not exactly a game-breaking issue, especially given that, at higher CLs, the item still has the exact same hardness and hit points it started with, so even if it makes it save, it's likely to go kaput from the damage anyway.
In other words, the benefits of higher CL for CL-indepent items are scanty at best, and hardly a reason to denounce the whole system.