We believe in selling our products to customers, not selling our customers to advertisers.
Converter does not send any of your data anywhere. It only communicates with us to update its exchange rates, and only sends limited technical data such as the version of Converter you are using; we purge this data after about a week. In the future, it may also include some information to help us verify your subscription, but that won't include anything more private than a random ID number. Apple also provides us with data about sales, usage, and bugs, but they anonymize this information before it ever reaches us.
We don't sell or give any data to anybody, though we hire other companies to store and process it for us. Anything Converter sends to us is secured during transport with industry-standard TLS encryption. We do our best to secure our systems, but we think the best way to protect your privacy is to not have anything worth stealing, so we just don't gather it in the first place.