Genshin Impact until these last few months had exactly what @onnekas@sopuli.xyz is suggesting on Google Play. You could redeem Google Play points for a voucher that gave you $3 off a real money purchase. Additionally, devs on Reddit would often post codes to give a set dollar amount off of a new app. I’m pretty positive that at least with Google Play, vouchers that can give $X off a purchase are baked into the platform in numerous ways.
I’m not about to suggest that anyone should do mouse/keyboard gaming with anything less than a proper mouse, but in a few cases where I’ve been without a proper mouse, the trackpoint has been indisputably better than a trackpad for gaming. It’s not even close. Mouselook via a trackpoint is basically joystick control and it works pretty much exactly how you’d expect. A trackpad is just chaos mode and probably constitutes a war crime if you’re forcing someone else to do it.
My app didn’t call out your response until tonight, so my apologies for the lateness of this reply.
As mentioned, I’ve seen app developers on Reddit give away discount codes to achieve lower purchase prices for specific users they wanted to privilege. I used one once myself for $5 off an in app purchase and it worked as intended, but that was long enough ago that I was still on Reddit, so who knows what the landscape of that looks like today.