Please clarify. Are you saying that you can contribute $4k-5k PER MONTH towards college out of current income? Meaning that you can pay $48k-60k per year towards college?
If so, and your child is a junior, then test that ability by NOW saving $4k-5k per month in a 529. That will let you know if you can sustain such a contribution for 48 straight months.
Of course, keep in mind that nearly all families have a few unexpected big expenses come up each year: dental work, health issue, etc, so be sure to take those into acct.