That absolutely makes sense and I think I understand what you're saying. You brought up some excellent points, but I still believe it is actually a terrific idea as long as you go into it with the right perspective.
I think what you're saying is that if you test yourself with the goal of seeing how much you can drink for the sake of "gaming the system", then yes, it is a complete waste of time and 50 bucks and dangerous. (My apologies if I misinterpreted your statements.) Anyone with that mindset will probably just gamble anyway and say "Oh well, I 'probably' won't get caught" or justify their actions in some other manner and drive anyway. Nothing will change.
However, it was more like a profound awakening for 100% of the people in my little group.
For example, when it was my turn to use the tester, I came home and had a couple beers during a 1 hour period just like we used to do after work on Fridays. I waited 20 minutes (as directed) and did the test. I could have been arrested if I had been driving. The next night I did the same thing during a 90 minute period. Could have been arrested. A few days later, I repeated the test with 1 beer instead of two in an hour. Could have been arrested. Next night: 1 beer in 90 minutes - probably could have been arrested considering the police probably have a more accurate machine than one that cost only $50. With food, without food, not much difference. Arrested. Arrested. No matter what I did the results were about the same.
In OK, a DUI is .08% but a DWI is .05%. Both have nearly identical legal ramifications.
The end result is that it scared the crap out of every last one of us and, where we used to think we were "OK" it made us realize the only "safe" amount of alcohol is ZERO.
It didn't bolster our sense of security, it actually destroyed our existing false sense of security. Everyone who participated were all basically the same age and we had always been told that one drink per hour was ok. That general guide proved to be incredibly FALSE.
That's why I spoke earlier about my embarrassment, shame and regret.