Shares of the online retailer slipped $12, or 1.5%, to $768 on Monday. The stock is now down nearly $80 from its recent high of $847 less than two months ago. The drop in shares of Amazon (AMZN) come as analysts are saying that this Cyber Monday is expected to be the biggest ever, hitting a record $3.3 billion in sales, up nearly 10% from a year ago.

So what gives?

Well, while near 10% growth sounds good, and would be great for a giant traditional retailer like Walmart (WMT), it would actually be relatively slow for Amazon. Sales at the online retailer are expected to rise 25% in the fourth quarter from a year ago. The expectation of huge sales growth is built into Amazon’s enormous stock market valuation of $365 billion, or 176 times its last 12 months of earnings. So a 10% jump would actually be a big disappointment.

In the past year, giant retailers, Walmart in particular, have put more and more emphasis on growing their online sales. Walmart and Target (TGT) this year offered bigger discounts on Black Friday and Cyber Monday to combat Amazon. Research firm Market Track, based on holiday circulars, found that Walmart was offering an average discount of 39% this year, up from 35% last year. Target is offering average discounts of 38% during the post-Thanksgiving shopping spree, vs. 36% a year ago.

This is forcing Amazon to match as well. It says it is offering deals on 75,000 items on its website this week. And this comes at a time when investors are betting that Amazon will be able to turn its massive sales into profit, as much as $4.8 billion this year, and $6.9 billion next.

The good news is that the fastest growing portion of its business, web services, is not as dependent on Cyber Monday traffic, or at least traffic directly to Amazon. Still that only makes up about 10% of Amazon’s total business. And if the company increasingly finds itself in even more of an online price war than its already in, investors may not be getting much of a discount on the company’s shares at all.