Why does ～なんてもんじゃない / ～のなんのって mean とても？


Both the following two expressions from my text book 完全マスター聴解N１ are explained
as とても（高い／人が多かった）:

> 高いなんてもんじゃないよ
>
> 人が多かったのなんのって

Could someone explain what they are based on/where they come from because
although I can try rememeber them as colloquialisms, they ought to based on
some conventional grammar.




The first sentence could be expanded to

> 高いなんてもんじゃないよ。むちゃくちゃ高いんだよ。  
>  It's not (just) huge. It's humongous.

and the first part would be written as

> 高いというものじゃないよ。

* * *

As for the second sentence, separating the sentence as

> 人が多かったの 何の って

the 何の is used to repeat the structure of the first part, but could be
replaced with anything, indicating that the speaker can't even say there were
many people, because "many" isn't enough to describe the situation. The って is
used to strengthen the speaker's feeling about what he said, as he is quoting
himself in a way, cf.

> 絶対危険だって

To compare the two phrases, let's take the sentence

> このホテルは汚かった。

Turning this into

>   * 汚かったなんてもんじゃない。
>   * 汚かったのなんのって。
>

the first means that the hotel was extremely dirty and the word "dirty" would
not be _strong enough_ to express just how dirty it was, whilst the second
means that it was dirty, ugly, etc. and no single word would be sufficient to
express the _various ways_ in which it was unpleasant.

A related phrase is

> 楽しい **ったらありゃしない**

which comes from

> 楽しい と言ったら、有りはしない

and also means, very roughly とても, in this case "it was as great as it could
possibly have been".

P.S. This use of 何{なん} is the same as seen in

> 電話なり何なり

(thanks, Tim).

If 何 is already used, one uses かん instead, as in

> 何だかんだ  
>  何でもかんでもない




The first sentence could be expanded to

> 高いなんてもんじゃないよ。むちゃくちゃ高いんだよ。  
>  It's not (just) huge. It's humongous.

and the first part would be written as

> 高いというものじゃないよ。

* * *

As for the second sentence, separating the sentence as

> 人が多かったの 何の って

the 何の is used to repeat the structure of the first part, but could be
replaced with anything, indicating that the speaker can't even say there were
many people, because "many" isn't enough to describe the situation. The って is
used to strengthen the speaker's feeling about what he said, as he is quoting
himself in a way, cf.

> 絶対危険だって

To compare the two phrases, let's take the sentence

> このホテルは汚かった。

Turning this into

>   * 汚かったなんてもんじゃない。
>   * 汚かったのなんのって。
>

the first means that the hotel was extremely dirty and the word "dirty" would
not be _strong enough_ to express just how dirty it was, whilst the second
means that it was dirty, ugly, etc. and no single word would be sufficient to
express the _various ways_ in which it was unpleasant.

A related phrase is

> 楽しい **ったらありゃしない**

which comes from

> 楽しい と言ったら、有りはしない

and also means, very roughly とても, in this case "it was as great as it could
possibly have been".

P.S. This use of 何{なん} is the same as seen in

> 電話なり何なり

(thanks, Tim).

If 何 is already used, one uses かん instead, as in

> 何だかんだ  
>  何でもかんでもない

