I have been receiving monthly checks from Google since 2003. My earnings are usually in the low to mid 4-figures.
My sites have been around for a long time and I have a great deal of traffic so that's a big reason why I earn 4 digits per month.
I promote my sites on social media, create YouTube videos etc. Making a lot of money with AdSense is all about numbers. The more traffic you have, the greater the earning potential.
My checks weren't always this large. I think my first month's earnings in 2003 totaled less than $20. However, as my traffic increased, so did my checks.
I cannot emphasize this enough. AdSense is NOT an overnight get-rich-quick opportunity. Even though this may look easy, please don't underestimate the amount of work I've put into my sites over the years.