This heathen thinks that tithing $1000/month when you can't pay your bills is fucking stupid now matter how pious you are!
Besides, in the long run you could tithe more by building your wealth and then establishing a trust fund.
I don't necessarily disagree, but as a tither myself I can hopefully shed some light on *why* it is so essential to some people. I think the stupid thing is spending more than you make, period. Tithing itself is not the problem, it just exacerbates it.
Some Christians (the only group I can really speak for) consider tithing to be a form of gratitude to God for the blessings he has given you. Furthermore, there is significant Biblical precedent that giving back to God should be the first thing you do, not the last. It's a matter of priority and psychology. Giving first to God, no matter what else is going on, shows through actions how important God and your gratitude to him are. If you give only if you have some leftover scraps after you've bought everything else that you want, well then you must not be very grateful right?
That's also why people don't defer tithing until after they've built up a persistent trust fund for tithing. Yes the trust fund would end up resulting in more money in the long run, but doing so would violate the give-first principle. It could also be (mis)construed as telling God how to manage his money, which presumes you know something he doesn't.
I don't necessarily agree or disagree with either of those thoughts, but hopefully that sheds some light on why it's not a simple "well I just won't donate money to charity until I can afford it" type of situation for some people. The problem here in my opinion is their spending habits in general, not necessarily their tithing.
It's also interesting to note that there's not really an explicit "you must give X% of your income to God" statement anywhere in the Bible. 10% has kinda become the default for many people, but it's not a hard-and-fast rule. It looks like this guy is giving more like 15% which is higher than normal, but he still doesn't want to make any cuts. Maybe he's calculating 10% of his pre-tax income. It's just interesting is all.