Is one allowed to concurrently purchase two items which are similar in nature (e.g. electronic gadgets) in order to compare them and subsequently return the non-desired item? The halachic concern would be that one of the sellers is incurring a monetary loss due to shipping costs and/or restocking costs. This question is most relevant for e-commerce shopping, since the consumer often does not have the ability to compare products in the same way that they could in a physical retail store. Thanks!
If it is clear that this is the common way shopping online is done, and the sellers are aware of it, and are willing to bear the loss for the chance of making a sale, it is permissible to do so. If it is not clear that this is the common custom then it is permitted to do so only if you notify the seller in advance that you are ordering from two places and intend to return one of them, and yet he is willing to sell it to you and ship the product. However, in a case where the seller is unaware of this, it is forbidden to do so because the seller offers the customers their money back on the assumption that most likely the buyer desires the product and will keep it. So in this case one should be concerned about the following issues, theft, Mi She'para (a Rabbinic curse to he who does not stand by his word, that begins with the words "He Who took retribution"), and Mechusar Amanah (unreliable) (See Shulchan Aruch Choshen Mishpat 204).