guardmytongue,
The flipside is that those in Kollel are more likely to have larger families. So instead of 4 kids in yeshiva, you may have 8. If you live in Lakewood, that’s $40,000/year in tuition.
Your mortgage may be less (lets say $1500/month = $18,000/year) and your groceries may be $1,000/month if you keep it really cheap.
That’s already $80,000/year (after tax money) and there are many, many more expenses.