@Cindy16 - almost right. AdSense ads are not affiliate marketing, so the money you get has nothing to do with the price of the product or service being marketed.
Rather, AdSense ads are the flip side of Google Ads (what used to be called AdWords) pay per click ads. Essentially, PPC advertisers who opt in to Google's content network agree to have their ads appear on publisher pages when those pages have content Google's algorithm determines is relevant for their ad.
The publisher gets a percentage of the money the advertiser bid for placing their ad.
So, for example (all these numbers are totally made up and have no relationship to Real Life):
Let's say somebody decides to advertise their service using Google Ads. They opt to include the content network and bid $5 per click.
A publisher has signed up to AdSense and has a page with content that is related to the service being advertised. So Google displays the advertiser's ad on that page.
A visitor arrives at the page and clicks on the ad. The advertiser is charged $5 for the click. Google keeps $4.50 of the revenue and the publisher of the page gets $0.50.
It doesn't matter if the service costs $100 or $100,000 — the driving force is the amount the advertiser bid per click. And, of course, the more clicks the ad gets, the more money the publisher will make.
So the trick is to find one of those "Holy Grail" keywords — relatively high per-click bids and relatively high search volume — and writing "unicorn" content — good enough that it doesn't run afoul of Google's Panda/RankBrain/Fred algorithm updates, but not so good that people stick around (because you want them to click away on the ads instead). That way you end up with a golden combination of content that attracts a lot of visitors without turning off the search engines, and that also inspires a lot of those visitors to click on the ads.
It's actually a lot harder than it looks. It takes a very delicate balance of content and page layout to pull it off. And it's a lot harder than it used to be, thanks to Google's ongoing crackdown on low-quality MFA (Made For Adsense) websites.