Retail website sometimes have inadvertent website glitches that result in enormous savings at the checkout.
Even if they honor the transaction, is it considered stealing? Should a baal nefesh stay away? Does it matter that the retailer is not jewish, there is no chance of chillul Hashem, and that others will take my place in taking advantage of the deal if I don’t?
If the retailer is not Jewish, then you are allowed to capitalize (pun intended) on the deal without a problem. If the retailer however is a Jew, there is room to say that the retailer knows that these mistakes happen, and he agreed to take such a risk when selling things online. Nevertheless, it is better to stay away from such things, from a simple angle of don’t do to others what you wouldn’t want them to do to you..