I found a response from an attorney on the subject. Remember the US doesn't have as much consumer rights laws as the UK does, so all you english guys shouldn't try to apply your law here
In internet transactions, online retailers usually get around pricing mistakes by having this language on their websites as part of the "conditions" for using the site:
"â€¦ Errors or omissions in descriptive, typographic, pricing and/or photographic representation are subject to correction."
Usually there is a disclaimer somewhere stating that, by using the site, users agree to certain terms and conditions which often include pricing mistake disclaimers. Court have found these to be binding contracts between the users of the site and the retailer. In most cases, the users of the site would be contractually bound to accept a pricing correction from the retailer.
In brick-and-mortar retail situations there are cases holding that retailers are liable for pricing mistakes, but only where the mistake is caused by the retailer and not by the fault of a third party.
This would make it hard to go after an online retailer even if they did not disclaim pricing errors on their website because often the website and pricing engine are run by third parties, not directly by the retailer. There are a few retailers that run their own sites such as Amazon but the vast majority of retailers subcontract with a website commerce provider to set up their retail website. Under these situations it is likely that the pricing mistake was caused by the third party and not the retailer themselves.
From a litigation standpoint it would be difficult (and expensive) to prove where the pricing mistake originated if the retailer blames the third party. In these situations the consumer has few realistic (cost-effective) legal options to force the online retailer to honor a website price.