There are several international insurance carriers that offer far more robust health insurance policies than INS. Some have lifetime limits of $5 million and they will pay no matter what country you are in when the expenses are incurred. Some even have reduced premiums if you specify that expenses will ONLY be incurred in one country or in Central America.
Note: While you cannot buy health insurance in Costa Rica from any other company than INS or CCSS, these other policies are perfectly legal to purchase and many have payment arrangements already in place with several private hospitals in Costa Rica. This is one way to get around one of the great monopolies of Costa Rica-INS.
You can do some research on this by Internet or contact Guardian Angels at email@example.com for some of your options with International coverage.