The concept you are talking about is a called a Denial of Service (DOS) attack. Typcially that is down with malware, there is another type that uses bots that is called a Distributed Denial of Service (DDOS) attack. In a DOS attack the malware overwhelms the capabilities of a website, email server, ftp server etc to the point where it fails.

If the number of people browsing the site do not overwhelm the site it won’t cost the company shit. Any CDN/web hosting company worth a damn will have the capacity to handle the black Friday weekend surge.