On the surface, the deal—Amazon’s biggest acquisition in its 21-year history—doesn’t exactly look cheap. After all, Amazon (AMZN) is paying $42 a share for Whole Foods (WFM), 27% more than what Whole Foods stock traded for Thursday, the day before the acquisition was announced.

Amazon is also paying a 15% premium above what rival supermarket company Albertsons reportedly offered to pay to acquire Whole Foods less than two months ago, a deal that would have valued the health food store at about $11.7 billion, or $36.50 per share, according to Bloomberg data. And it’s paying more despite the fact that Whole Foods stock had since fallen more than 9% in the time between the rumored Albertsons bid and when Amazon announced the deal.

Yet considering the soaring value of Whole Foods’s stock in the not too distant past, the online retailer could have easily had to shell out a lot more to own the grocery company. Had Amazon tried to buy Whole Foods three and a half years ago, the deal would likely have cost at least double. Whole Foods stock peaked at just over $65 a share in October 2013, valuing the company at $24.3 billion; at market close this Thursday, the stock traded for about half as much, at $33 a share.

Whole Foods’ stock drop was a major reason that activist investors were pushing the grocery chain to sell itself in the first place.

Even after Whole Foods stock surged Friday on the news of the sale, Amazon was still getting a 36% discount compared to what the healthy retailer was worth back in 2013.

In fact, had Amazon paid the same premium for Whole Foods then that it’s paying now, it would have spent about 125% more, or about $30.8 billion.

And ultimately, Amazon and its investors may have gotten an even sweeter deal: Amazon stock rose more than 3% after it announced the deal, boosting the online retailer’s market value by about $14.5 billion—even more than the what it is spending to own all of Whole Foods. In that respect, the deal is already paying for itself.