I use https://exodus-privacy.eu.org/ to check for trackers, ads and "malware".
[1] Far too often, the apps there are "OK, but...", clearly the work of a someone building a quick "works for me" or someone learning how to build apps. For some tasks, "just OK" is good enough. More often it just isn't.
So if someone like me had incentive for free metronome. I'm pretty sure there are also tuners out there.
Still, 1$ to support an app is really legitimate and sometimes gives more incentives for the developer to maintain it or add features.
An important distinction so many entrepreneurs fail to make. Don't enter a saturated market without anything new on the table if you intend to make money.
The problem with this particular market is that musicians can mostly tune by ear. Most will have a dedicated tuner next to their instrument and worst of all these apps don't perform as well for a variety of reasons not least of all that the response of the device might be off.
Most musicians can tune "relatively" okay, but do not have the ability to tune "absolutely" (perfect pitch).
Here is an example of perfect/absolute pitch that very few musicians have. This is the skill one would need to be able to not use a tuner at all > https://www.youtube.com/watch?v=dw3-k9 (Jimmy Kimmel Puts Charlie Puth’s Perfect Pitch to the Test).
I find the idea that $1 is a "hard sell" laughable, but unfortunately for software devs that is the world we find ourselves in when trying to monetize an idea.
> I find the idea that $1 is a "hard sell" laughable, but unfortunately for software devs that is the world we find ourselves in when trying to monetize an idea.
and it's hard sell because you can just pick any of them, test to your liking and pay for one after using it.
Plus, it's much less fiddly to handle than balancing a phone and a guitar :)
Ultimately, it's a matter of taste, and what you use them for.