Sewing machine reseller in Slovenia. I started to work with them in May 2017. After 1 Month, they reached biggest income, since they measure conversions.
Below are data from April 2020. Despite COVID, we saw enormous growth in online sales:
  ➜  compared to April 2019 we got 160% more users
  ➜  cost went up by 125%
  ➜  they had over 300% growth in sales and revenue

E-commerce shop with children’s toys and Christmas lights. Data from Q2 & Q3 2020, compared to same period in 2019 (they were managing adwords alone back then)
  ➜  138% growth in users
  ➜  85% higher costs
  ➜  22% lower CPC
  ➜  350% more conversions
  ➜  221% more revenue

One of top sellers of garage doors and shutters in the UK. We started working together in NOV 2021.
At the beginning their cost per lead was around 130 GBP, some campaigns even had CPA over 300 GBP
Results:
  ➜  60 days before we started CPA was 133 GBP, conv. Rate 1.04%
  ➜  3 months after we started CPA was 54.3 GBP (-60%) and conv.Rate 3.39% (over 300% growth)

In the first 3 months after optimization CPA went from 133 down to 54 GBP!