Amazon (AMZN) reported third quarter earnings on Thursday that missed on profit but exceeded Wall Street’s revenue expectations, with sales getting a boost from Prime Day deals, the implementation of one-day shipping and a bevy of new Echo and Fire TV devices.

Yet the retail giant’s first earnings miss in two years sent Amazon’s shares, which ended trading at $1,780.78, tumbling over 7% in post-market trading — washing out $80 billion in market capitalization.

Here were the key numbers, according to a consensus forecast from Bloomberg:

• Revenue: $70 billion vs. $68.7 billion expected

• GAAP earnings per share: $4.23 vs. $4.58 expected

• Amazon Web Services: $9 billion vs. $9.19 billion expected

Much of the quarter’s upside was driven by Amazon Prime’s higher membership price tag, and the rollout of free next-day delivery announced in April — leading to a 24% boost in sales and cash flow from the comparable year-ago quarter. Prime Day, Amazon’s annual sale bonanza that took place in July and saw the retailer move over 175 million items from its virtual store, was also captured in the quarterly figures.

“We are ramping up to make our 25th holiday season the best ever for Prime customers — with millions of products available for free one-day delivery,” said Jeff Bezos, Amazon founder and CEO. “Customers love the transition of Prime from two days to one day — they’ve already ordered billions of items with free one-day delivery this year. It’s a big investment, and it’s the right long-term decision for customers.”

At least some of Amazon’s sales growth was offset by higher marketing and shipping costs. Amazon previously warned that the investment in one-day shipping was exceeding the $800 million it originally allotted for the task, and intended to spend at least as much in Q3.

It appears much of that investment will drag on fourth quarter and full-year expectations, with Amazon forecasting Q4 net sales to fall between $80.0 billion and $86.5 billion, representing 11% and 20% compared with fourth quarter 2018, subject to foreign exchange fluctuations. Operating income is expected to be between $1.2 billion and $2.9 billion, compared with $3.8 billion in fourth quarter 2018.

The forward guidance fell below what analysts at Bank of America-Merrill Lynch had forecast — helping to drive down the stock in after-hours trading.

Calling the move to one-day shipping “encouraging,” analysts at Societe Generale wrote in a recent note that the initiative may have helped spur growth in sales. However, “to achieve its ambitious plan to shift to free one-day shipping, we think Amazon needs to add capacity (i.e. fulfillment centers and infrastructure) and make some changes to the supply chain,” said the firm, which rates Amazon’s stock as a “Buy.”