I worked in a SaaS company selling an A/B Testing app where I saw a lot of tests and their outcomes from different clients.

Of course there are the low hanging fruits, which scored the clear success. Most of the tests although were not a clear success, but just a slightly better conversion rate.

Multiple tests applied after each other slowly increased the overall value. If taken the advice not to implement the changes of the small success, the overall amount would not have changed.