The only meaningful measurement of CPH is how many components you can put down over the course of a run. Say I want to do 10 of my PCB sets with around 300 components total per PCB set (a few different PCB's that go together). 3000 parts total.
The actual placement time is about 1 hour - 300CPH. But if I look at the whole day - I can only get about half that if I am lucky. The problem is that while I am placing parts, I cannot prep the next PCB, manage the re-flow oven, inspect the previous PCB, manage the parts, answer a phone call, go to the restroom, etc. With a 300cph machine, I can be doing all the other tasks needed and the machine would only stop long enough for me to load the next PCB. That would be a true 300CPH line.
I learned the details when I had my machine shop. We were very focused on how fast the machine could move and never paid much attention to how slow all the other processes were. I was about to drop $500k on a super-fast machine when I realized we can triple the output of our current machines by feeding them faster. For only a few $thousand I dramatically sped up the process by being able to keep our slow machines busy 99% of the time. My only concern was how many parts can I get in a day - NOT how fast the cutter can shred the metal.
In the case of P&P, the concept is similar. I would say that a 300cph machine would at least double the output for someone coming from a fully manual process, maybe even triple. You will be placing parts while you eat lunch, talk on the phone, count parts, day dream, whatever.