[/quote]
What if the women wants more (
, its one of those wonders of life expecially after the first one), but the man doesn't, and why isn't financing an issue? Everything costs a lot of $ these days, he doesn't want to live on charity, and wants to send his children to the best Yeshiva's. (thats after the fact that he has at least 2 children (One male and one female) which can reproduce (G-d willing), which fullfils the Mitzva.
[/quote]
Talk about how many kids you want to have before you get married so you don't have this problem.
The sin of wasting seed is very serious. It's akin to murder at a more refined level of looking at things.
So we don't cast aside this prohibition lightly for things like money and convenience. Life takes precedence over these things.
There is also a more general point to be made here:
As Jews we believe G-d runs the world and if He feels you are ready for the gift of the child and His torah says you should have the child, He also knows that you can handle the child and it's an affront to Him to say you are not interested in His gifts or that you can handle it financially or otherwise in your opinion. In G-d's opinion you can handle it so "step it up a notch and make it work" is what we'll tell him in most cases.