https://www.nickkusters.com/en/Services/Thomson-SpeedTouch
I just added ads and it's made 50-300 a month (had ~1000 unique visitors a day for the last 8 years).
Added https://www.nickkusters.com/en/Services/UPC last year for a different brand model
And
https://www.nickkusters.com/en/Services/DownloadFundaImages for the Dutch real-estate market
And a few years ago, I reverse enginered the encryption of the Wordz game and post the new game 20-30 seconds before the new roud starts, and more: https://www.nickkusters.com/nl/Diensten/WoordJacht/
This combined is my hobby/fun website. It used to cost €300 a month in server fees; it's now down to €80. Over the lifetime of the site, I probably broke even :) But it's still used daily, generating ad revenue, and if I had put in time to cut down cost, I could have made some money.