If you want to know the overhead of TDE, you can use (distributed) replay. That is, first capture a reasonable amout of workload with a trace. Then set up a test machine where run the workload multiple times with help of Replay. For some of the runs you have the database enabled with TDE, and for some not. Measure CPU as suggest by Gail and others in the thread.

I have never used Replay myself, so I cannot give the exact details. But it goes without saying that running these tests will keep you busy for a day or two.