Why have subscriptions for pro?

We sell subscriptions since all our costs are ongoing (data processing, servers, testing, translations, development, marketing, support, etc).  We've tried the "low price/high volume" approach with banner ads, video ads, cheap subscriptions and one-off purchases, and we are not covering the costs. This is not sustainable.  Now we're going premium with premium data at sustainable prices. See the Pro Version help page for more info.