And $1500 is not expensive for a game engine, or really any type of professional content creation tool.
The free version is very capable and unless you make more than $100K dollars with it, you don't have to pay.
"Unity Free, which include the free platform add-on products, may not be licensed or used by a commercial entity with annual gross revenues (based on prior fiscal year) in excess of US$100,000, or by an educational, academic, non-profit or government entity with a total annual budget for the entire entity (based on prior fiscal year) in excess of US$100,000."
Sure, GDScript is poorly documented and isn't really python, but it's not that hard to find the undocumented features (search the github code), and the fact that it compiles to pretty much any platform means it's a rather small mental investment for a large gain in deployability.
Just try to imagine how much money you would need to charge for software to be able to live from it and pay all running expenses.
I just would like that they settle their issues with Xamarin and update they .NET runtime to a more modern one.
[I'm one of the founders]