Doesn't appear you've really crunched any numbers (acting on...

Doesn't appear you've really crunched any numbers (acting on emotions perhaps??). APT currently have a 2.2m Aus user base and will report about a $5m net profit for 2018, for an average loan size of $150 we are talking $5m profit on $330m in loans, that IS low margin.
On that simple metric alone even if next year they grow a 20m US user base (more unlikely than likely), we are looking at a net profit of MAYBE $50 mil next year as an absolute MAX (you get similar numbers of you calculate it properly, i.e. $150 average loan, 10% defaulting, APT makes 15% per defaulted client per year). To support it's current $3Billion valuation the market is pricing not only achieving that, but DOUBLING earnings YEAR after YEAR, reaching 300million in only 3 years before maturing (I've run these numbers with a discount rate of 11% and terminal growth of 2.8%).
Anyone long APT is in a negative EV trade. Wouldn't be surprised if this halved or even 1/3 in the coming months once market properly digests earnings trajectory, even in the case this is a solid company - you'll be able to get in cheaper.