They use counterfactuals, so they are comparing apples to apples. There are other ways to do it. One of the easiest, yet most effective way is matching. You can

They use counterfactuals, so they are comparing apples to apples. There are other ways to do it. One of the easiest, yet most effective way is matching. You can match your observations with various statistical models, k-means would do a very good job here, and then run a regression. Compare parameters and you are done. It's not a rocket science.