As mentioned above, it's not a cut-and-dry comparison. Regardless of the retention of freedom, (which in fact many females in relationships claim to have, and in some cases even more freedom), it was the comparison of the males role in society as the the provider as the money maker, with the concept that in very general senses: it will cost money for a male to have sex. That being said, I am not implying that it doesn't cost a women to have sex, but socio-historically speaking, it is the monetary burden of the male. The idea of prostitution in a very broad sense, is a simplification of this concept to bare basics. (Again, a broad sense: leaving out the issues of diseases, unwanted pregnancies, mental effects and trafficking).

...ehm, the hand and the internet?

English Forum???!!?? No way, that's pervy, you must be reading the sex-obsessed threads

Oh come on, everybody's doing it!

and there are none of those on the EF, right?

Wow this is funny.

The model was made by Porter who is quite famous for doing the opposite - explaining things in simple terms. I have no problem to admit that I like simplistic models.

But that's of course to banal for people like you... which is in short why scientists and engineers run the world, get all the money and the women...

I like simplistic models when they explain complex things. A five input to one output model isn't complex, especially when it seems that all five inputs influence the output to the same degree. But the diagram doesn't make that obvious. I took a didactics course at uni and this flies in the face of all the most trivial rules.

If that's a good explanation, I'd like to see a bad one.