It's not uncommon for online and even brick-n-mortar stores to have terms of sale online that include disclaimers like "not responsible for pricing errors" and list "order cancellation" as a remedy that you are willing to accept as part of the terms of sale.
Though I've seen a number of "pricing errors" where companies honored the sales made prior to them fixing the error, just to not have to deal with a public backlash.
I know Best Buy has done this at least twice.
- - - Updated - - -
yep I remember that, diaperbuys.com had an xplus case bogo with free shipping. I think that was what they wanted to do, but were just not expecting the response they got. The "inventory that had been allocated for the sale" was depleted within 36 hrs, and I recall a few here saying they had hit them up for over $1,000 in diapers. (IC that were going to be using that many cases in the next few years anyway and had the space to store them) I got four cases of size Large (36 diapers per case, 144 diapers total) for $109 shipped. It was an incredible deal. I would have bought twice that much or more if I'd had more room to store them at the time. $1,000 would get you 1,333 decent quality diapers. (37 cases!) For a lot of us that seems like a bottomless pit, but that's just 3.6/day for a year. So only half a year's supply for a full IC person who goes through 7 diapers / day! That'd drop their year's diaper bill from $4,000 to $2,000 if they had 2 grand to invest in a sale like that.
(I suppose 7/day is an average number for lower quality diapers though... maybe the daily average is more like 4/day for those. So close to a year's supply for $1k)