Operating a marketplace for buying and selling balances remaining on private label prepaid cards is the business of Raise, which has received $81 million in funding since 2013. Unlike other companies that see opportunities to generate revenue from the estimated $100 billion a year in unwanted prepaid card balances, Raise does not buy and then sell cards. It performs a service like eBay or Stub Hub, taking a 15% commission from sellers. The private label prepaid card market has three components — purchased as gifts, issued as store credit, and issued as a merchandiser’s credit. Collectiv...