Are you able to share some details? How often did you have to get new IP addresses? What about user agent? Were the scapers "straight to the point" like amazon2csv (ie: make a request directly to the search page) or did they have randomized behavior (eg: re-use sessions from time to time; click a random link on the page; start from the homepage...)? Did the scrapers ever went against amz's robots.txt directives (eg: interacting with the cart page)? Ever heard from amz itself about your employer's activities on their site?

There are services dedicated to scrapping which can take care of proxy-ing your requests so you don't have to worry about IP bans.

For example, Scrapinghub's Crawlera (the guys behind the Scrapy python lib)

Same here. Scraping their search results page is easy if you have a bunch of IPs. No manipulation or workarounds needed(ie headless browsers, ensuring your http headers look like a real user).

I have not scraped a ton of actual individual product pages though so cant testify about scraping that. I do remember it might have been harder.