The pay scale I'm on is a little different, we'll discuss line pilots here.
You said that you guys are paid for duty time, which would mean that you are paid $35 an hour for every hour you spend on duty. That's how we're paid; if we're only duty, we're paid $12. There is no difference between flying and not flying, just a straight $12 an hour. We have our guarantee set on a 40 hour duty week that is predicated on $12 an hour (ish, it's actually $11 and some change I think). Most pilots in my base will never hit 40 hours of duty during the week, but we are still paid by the duty hour.
You are paid by the flight hour, and your guarantee is based on the flight hour. You have two pay rates: $35 and free. In a given trip, if you are on duty for 14 hours and you fly for 6, you will be paid $35 multiplied by 6. If you happen to not make it to 75 (or whatever) hours of flight time in a given month, yes you are paid your min. guarantee for the month.
Our pay scales are COMPLETELY different. If you were paid $35 an hour for every hour of duty you worked you'd be filthy stinkin' rich; and that was what you wrote. Here, I'll quote it for you...
121 pilots are also paid while on duty, much like AMF pays it's pilots. There's just also an opportunity to pay above and beyond that salary at an airline.
So if you were paid like I was, then you'd be paid $35 an hour for every hour you're on duty. Again, assuming the 14 hour duty day multiplied by 4 days example you'd be paid for 56 hours, but you're not. You are paid, and your guarantee is based off of when you're actually flying the aircraft.