What percentage of your users are monthly active users? What percentage (of the monthly active users) ended up paying? How much do you charge per month? How did you figure out what to charge?
Initially, I just wanted to make the service pay for itself (hosting, dev., data mining costs) and allow me to dedicate some time to provide support to users, so I asked myself, as a dev/company, how much would I pay for this service. I started with €80/year, and doubled the prices a few months later, to €160 (€13/month). The price increase seemed like a good business move, and surprisingly, the number of sales improved as a result.
Some live stats http://ip-api.com/docs/statistics
Assumption is that every IP (all 4.3 billion) had about 100 bytes of data stored about them. That is ~430gb of storage runs you $30/month. The 10 billion queries to that storage costs about $360/month. ($.0036 per 100,000 transactions)