Please explain the end of this conversation, especially the あってこそ part of it

Question

I've taken up reading the manga "Fruits Basket", with the intention of trying to understand every word and grammar point if I possibly can.

There is a conversation, starting on page 27 of the first volume, between Shigure and Yuki. They are cousins, sharing a house. Shigure is an adult, Yuki is a high-school student. They are not very good at house work like cooking and cleaning. In this scene they are walking through a forest, returning home from dining out:

[紫呉] あーあ、もうこんな時間か。毎日夕食が出前か外食だと疲れちゃうなぁ。

[由希] じゃあ紫呉が食事作ってよ。

[紫呉] 作ったって文句言うじゃないか君は。

[由希] カレーの中にたくあんが入ってれば文句の一つも言いたくなるよ。

[紫呉] 由希君は頭はいいくせに家事一般だけはだめだし、やっぱだらけた男二人暮らしには“花”が必要だねぇ。

＊　花ってなす女性の事さ。

[由希] 気楽だね紫呉は。

[紫呉] 何を言う。花あってこその男じゃないですか…

(Conversation ends here as they spot the main character nearby)

My problem is mainly with the last two lines there.

1. What is Yuki saying, exactly? It seems to mean something like "You live comfortably, Shigure", but I don't understand how it relates to what Shigure said about needing a woman around the house.
2. What is Shigure saying?
   • What does 花あってこその男 mean? I tried to look for similar expressions and it seems that [noun]あってこその[noun] is not uncommon, but I can't figure out what it means exactly.
   • What confuses me even further is the じゃないですか at the end. I'm not sure if it's a genuine question or the common rhetoric question that is really an assertion...
   • And so, I'm not sure whether the 花あってこその男 refers to Yuki or to Shigure himself.
   • And how does it relate to what Yuki was saying?

Edit

Here are a few similar あってこその phrases that I picked off Google, but couldn't really understand:

• あの時代あってこその今
• 人あってこその環境省
• マイナスあってこそのプラス
• 失敗あってこその現在

Note that in none of them is there a particle before the あってこそ, and there is a の following it.

Note also: the なす in the footnote about 花 is suspect - this part is written in handwriting so it was hard for me to decipher. Nevertheless, Shigure is absolutely talking about needing a woman around the house, as by the end of the chapter, they get one - Tohru Honda, the main protagonist.

Answer 1

The AあってこそのB(だ) means something along the lines of

B wouldn't exist without A
B wouldn't be B without A
B cannot bring out its full potential without A

The じゃないですか here is rhetorical, so the full meaning is something like

Men wouldn't be men without flowers(women), would they...

あってこその is fossilized to a certain extent (i.e. a fixed expression), so it might be easiest to memorize it as is. The fact that が is usually missing after A also witnesses slightly archaic grammar.

Answer 2

AあってこそB means that B exists due to A. The pattern is Verbて＋こそ. The first example I found on the interwebs

親になってこそ、親の苦労や気持がわかる。

B/c he became a parent, he understood the struggles and rewards [of being a parent].

You can of course use this with NOUN+あってこそ as you stated, or NOUN+いてこそ in case of a person. A quick google search came up w/ some cheesy DVD called あなたがいてこそ. The B in this case, being implied as "something".

That should help you understand the last line, although I admit that the footnote 花ってなす女性の事さ has thrown me.