Okay, so here’s the thing: the ‘freemium’ model is always going to cause friction, the user will be using the app and suddenly run into an apparently arbitrary paywall and that’ll almost always solicit some kind of ire along the lines of “I want to see this thing, this thing is already there, but now they’re asking me to pay for what is already constructed and therefore has zero marginal cost to the developer” (or some inchoate variation thereof). Basically it generates frustration.

My take is that this is a fair app for the usage case you posit: determining sunlight exposure in regions where not much is available. Other use cases come to mind: for example beach-goers who are keen to make sure they don’t overexpose themselves but gradually build up a tan. It’s data they can piece together themselves numerically or (to be perfectly honest) that being humans who have evolved for millennia under sunlight, we can kind of intuit ourselves.

I’d say it’s a roughly 1.99 euro purchase fee for the ‘trends’ feature. It may even be a 1.99 euro for the app itself rather than half-free half-paid, but it’s definitely not something I want a large recurring subscription for. I can look at the sky and I can look at my skin, and I can figure out the rest. The only value is in quantifying it, and so the whole thing is meaningless unless it tells me something I don’t intuitively already know.