I would never buy this app for more than $9 - there are free alternatives such as Rectangle. $9 is low enough I'd consider it if it has some extra features or polish, but definitely not $49 or $79.
FWIW I paid roughly $25 USD for a lifetime license for BetterTouchTool about 5 years ago, and I still use that daily. Only going off the description, BetterTouchTool seems like mostly feature overlap (not fully) and more flexible version of OP’s app. With a free trial model like what BetterTouchTool uses I could easily see myself spending $49 USD on a tool like that today. It would obviously have to be as mature as BetterTouchTool and not brand new without as many features and polish like OP’s tool, but probably OP can start to increase the price over time to something more in that ballpark as more features are added without much chagrin.
Also FWIW, I tried the free/FOSS tools like Spectacle and Rectangle before eventually deciding on BetterTouchTool for its flexibility with key bindings and wide swath of api’s that they can be bound to.
I've been steady user of Rectangle for years - coming from windows, it still amazes me how native Mac doesn't have a good built in system.
OP - Rectangle is pretty well known, open source, and maintained - it might be worth adding a comparison chart so prospective users can understand what makes your paid product worth choosing a free offering.