Yes, but to be fair it's awfully hard to find a free app that does the same without bloat due to any kind of ads. I'm going to buy this app just because of frustration due to that.
F-droid often has nice apps, but too often, they are just not good enough for what I want or need[1]. In that case, I'll gladly pay on the play-store because the paid version is nearly always (but certainly not guaranteed to) have less or no trackers ads, and malware included. The free apps far too often do.
[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.
https://tick.talaviram.com
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.