That's a faulty conclusion. Being a professional designer has no bearing on how much time you spend designing something.

In fact, you could assume the opposite: that, because he is a professional designer, it took him less time to design the app than it would've taken a "layman". (I'm not forgetting about the perfectionism of many designers, mind you)

It has incredible bearing. Let's presume it took him 1 hour to design the site. (It surely took dozens or hundreds, including modifications and improvements, but play along.) That 1 hour isn't just 1 hour. It's 1 hour, plus the 5 or 10 or 15 years he has spent living and breathing design, refining his abilities and sharpening his understanding of the craft. He can do a singular design faster than a "layman" because he has spent a significantly greater amount of time on Design in general.

Umm, yeah. It still took one hour of his time, regardless of how much experience he has. If someone rips of this idea, and he loses out, he has lost one hour of his time; not ten years.