To be honest, I don't think it'd make a blind bit of difference.
It would sell out eventually, and while it might get reduced, it won't really effect either Zavvi's or Disney's bottom line. Zavvi are simply the retailer, they have little to no say over artwork or contents of their products any more than Waterstone's or WHSmith's do over the cover and contents of a book. If they end up taking a big hit on one or two products, it'll barely register and even then, those costs will be passed down to Disney. A lot of companies work on a margin where 50% of the stock has to sell at the asking price to turn a profit. Anything after that is pure profit no matter what.
When you're talking small numbers like 3000 for a Disney/Pixar steelbook, it's hardly a big ask to hit that target.
Usually titles are often on sale or return (especially when it comes to Disney), so if Zavvi are left with a stupid amount, they just go back to Disney for a credit/refund. We know this has happened to some degree as Disney Rewards were offering several steelbooks this week alone for a few hundred points.
No amount of lost sales will bother Disney HE in the slightest when they're making millions from Marvel home video releases and cashing in time and time again by redesigning their existing classics range and adding O-rings which collectors go mad for. Bare in mind, there's still a handful of these classics unavailable in the UK which they're not bothered about either.
I can't see them changing any time soon.