The business model of Topps is double. Digitally, it's a standard "freemium model", where you can get more coins making small purchases via App Store or APK store. $0.99 will give you 25,000 credits, enough for a bunch of packs, or you can spend up to $99.95 on 1,350,000 credits and be Mr. Suitcase :-)
"Off line" however, lies also an interesting spin off: An often despised hobby, the card collecting industry has been lagging since 1990. But this apps have helped to their revival. Several topps physical sets this year carry promo codes to be used in the digital apps, and sometimes there has been promos in the digital apps that have given as prize physical sets from the Topps online store, like posters, uncut sheets or oversized cards. The frontier is getting thinner and thinner everyday.