They don't have unlimited shelf space, that's what Featured tab is, it showcases new apps and stuff every day.
Uh, you're talking about
featured product shelf space. That's not the same thing as limited (absolute) shelf space in a retail store. You're making an Apples to Oranges comparison, too. A retail store can only display a limited number of units for a product on the shelf, and keep a limited on-hand of a product (in back), because they are bound by the physical dimensions of the item and the space their store takes up. The App Store only has to stock
one of every app. It's data -- they are copying what they have to your device, so have
unlimited on-hand. Their customer-facing shelf space is limited only by the capacity of their drives in their servers. A retail store can only hold so much of any one item. The data density of computer storage is several orders of magnitude different than retail product as far as revenue per cubic inch.
"Featured Product" space is limited for the App Store, as you said, but that's
only Featured Space. You still have the rest of the (theoretically unlimited) App Store. Your metaphor is flawed. It would be like me going to Target and claiming only the stuff on the middle-of-the-aisle displays counts as "shelf space".
Even when comparing the limited "shelf space" of the Features Apps apps section to a retail featured-products display, Apple has the advantage. Their storefront is virtualized. They can write a script to rotate the Featured Apps around however often they want at the push of a button (or even automated). A physical store changing their featured products means having paid employees actually go to the high-traffic location and physically remove one product to stock another in its place for better visibility.
They have to rent/buy storage, rent physical space or build it to host servers, pay utilities, etc.
As I said in my original post, and you conveniently ignored in your reply, the differences in cost to retail a physical product vs. an app are
huge. An app is a computer file on a web server, in a data center. You could host
millions of apps in a room the size of a small bedroom, maintained by 1-2 people. All you need is bandwidth to deliver the goods and power to keep the servers on and cool. You cannot run a physical store that features this variety of products in the same space, you would have to pay for a much larger plot of land, and another 30-50% or so on top of that to allow parking for your customers to shop at your store. You would need a larger staff of people on hand at all times to run this store, too.
There are costs to develop the App Store interface itself and redo it occasionally, but these are not expenses that are ongoing constantly when open for business like your hourly employee headcount at Best Buy.
If you're seriously going to argue about such blatant physics here you're free to make a fool of yourself.
Edit: I also forgot about the logistics involved. Apple's App Store gets new products proactively submitted to it by makers. A physical store has to manage distribution centers (more real estate!) and sometimes private fleets of trucks and drivers (more payroll expenses!) to get the product to their stores. As a virtuallized storefront, Apple has a clear advantage here. They have a much smaller number of locations to serve a larger number of customers, and does not have to worry about managing inventory in a way to keep the product available, easily replenished, and not overstocked, effecting sales of other items.
