I was lucky enough to get the mispriced nikon 35mm lens
Sure.
Under SoGA, prices are an “invitation to treat” – there’s no obligation to sell at an advertised price until they’ve agreed to the sale contractually (hence the carefully worded boilerplate someone posted here earlier). If they take your money however, then agreement to the contract is implicit; to wit, they’re then legally obliged to complete the sale. So on the face of it, Amazon are perfectly within their rights here to say “oops, sorry” and cancel the order as the contract was never accepted.
What I’m not sure of is how, if at all, this is affected when someone else has an identical order honoured. Hmm.