If you haven’t already paid to upgrade to TuneIn Radio Pro, then chances are you won’t be doing so anytime soon. The popular internet radio app just got a massive price increase from $3.99 to $9.99 for no apparent reason, making its free, ad-supported counterpart look like an even more attractive option.

TuneIn Radio Pro has been a surprising success on both Android and iOS. It has over 50,000 ratings averaging at 4.3 stars in Google Play, and between 1 million and 5 million downloads — and that’s impressive for a paid Android app, particularly one that can be enjoyed for free if you don’t mind the ads.

But it may not be so popular in the future, thanks to a surprising and unexplained price increase to $9.99 on both platforms.

Where mobile apps are concerned, that’s a lot of money — especially on Android. Even top games like Minecraft, Grand Theft Auto: San Andreas, and Gameloft’s excellent new shooter Modern Combat 5: Blackout can all be had for under $7 each. So, what’s the deal with paying $10 for free internet radio?

Well, it’s thought that TuneIn may be trying to dissuade people from going pro. It’s certainly possible that the ad-supported version brings in more revenue than the paid version, and so the company could be trying to push new customers towards the free TuneIn app instead — without pulling the paid version altogether and frustrating those who already bought it.

On the other hand, it could just be a mistake.

We’ve reached out to TuneIn to see if we can get a reason for the price increase, and we’ll update this post when we get a response. In the meantime, stick with the free version.