By limiting the profit margin for insurance company's and increasing the number of insured, basic economics tells us, by simple mathematics, costs of premiums will decrease.
Secondly, the removal of pre-existing conditions will reduce the amount one pays out of pocket. Most company's pre Obamacare would require a 90 day probationary period before insurance was offered and if one went without coverage for more than 62 days they fell into the pre-existing clause. There is no synergy with this. Now having that removed it will reduce the anxiety associated with the whole process therefore reducing the amount of stress put on the population reducing the visits and medications.