49% could be the high-water mark; we don't know yet. If Amazon doesn't get a grip on the counterfeit product problem, sales could plummet. The switching cost to a new retailer is low.
But Amazon's war chest is near infite. Jet had half a billion in funding but was barely making a dent (while bleeding money) against Amazon and its unprofitable for anyone else pricing. Amazon barely makes a profit with their streamlined system so how can anyone compete with that.
And we've seen what they can do when a competitor emerges like diapers.com. They bury them in the ground Walmart of the 90s style.
As could have been 25, 26, 32, 35, 37, etc
If you were a betting man, would you bet 49% is a high water mark?