I'm sure Apple would prefer people to come in to the shop, have a look around, then buy a product from anywhere. They still get the same mark-up on the product, so it makes no difference to them. If I went in to *any* shop to have a look at the products and was asked to leave then I would make a point of never buying anything from that company.
The Apple Store is a showroom for Apple's products. It is designed to be an interactive experience so people can try before they buy. Yes this costs Apple money in leasing the building, furnishing it and staffing it, but this is an investment. You only have to look at Apple's profits to see that it's not exactly doing them any harm.
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moto