Unless you qualify for an exemption, you will be subject to a tax penalty for any month you are not covered under a qualified health plan.
The Tax Penalty for 2018 is 2.5% of your total household Adjusted Gross Income, or $695 per adult and $347.50 per child.
The tax/penalty can be considered an opportunity cost of purchasing your health insurance. In other words, you are foregoing the $2,085 (savings) off the cost of health insurance if you chose to secure coverage.
Though not a huge incentive, in your example, $1,500/month or $18,000 per year would actually be net cost to you of $15,915.
No doubt, that is a lot of money. Yet your exposure to a catastrophic loss because of unforeseen medical expenses to you or one of your family members is exponentially higher.