Paraphrase- It is argued that taking proactive measures to avoid falling sick is better than to treat it afterwards. Finding the cure and providing medical services after being ill could be exorbitant and therefore, money should be spent on preventive measures. Above is correct. An 's' needed to be added to 'afterward'. You could also replace 'to treat' with 'treating' to improve it. An alternative briefer paraphrasing is: "Preventative health care is far more cost effective than curing or treating diseases.