The obvious answer is, how does Amazon do it? They've figured it out, so everybody else needs to figure it out to compete. And they need to figure out how to do it better and cheaper. Easier said than done, of course.
I'm a Prime member, and I'm pretty hooked on the benefits. But what concerns me is Amazon doesn't so much offer sales as they match the sales prices of competitors. If I can, I want to reward the competitor who actually lowered the price, not the reactionary business who only lowered the price because they had to in order to compete. And what happens when the competition no longer exists? Is Amazon still going to benevolently keep prices low? Of course not, they are going to charge whatever the market will bear. They are a business with a profit motive, they won't keep their margins razor-thin forever.
That's a common refrain from us bargain hunters: "Shipping kills the deal." We don't want to pay for anything. I often search for coupon codes before I place orders, just to make sure I'm not missing out on percent off/free shipping/etc. deals that may happen to be floating around.
Odd when you think about how everything old is new again, we are going back to the early 1900's model of ordering merchandise from a catalog, just now the catalog is on a computer/tablet/smartphone screen and virtually endless. Also, with the advent of e-mail, there were predictions of the demise of USPS, but now they are a vital part of the retail shopping infrastructure, providing "last mile" delivery service, and even Sunday delivery for Amazon.
Remember Service Merchandise? Even though Service Merchandise went out of business about 25 years ago, I think that retail business model would fit very well with today's online ordering. You wouldn't even need a showroom, just a storefront and a warehouse of merchandise behind, with a conveyor belt in between. Order online, ready for pick it up in ~15 minutes, no wait, no shipping charges.