$3000 means nothing for big companies, especially if we consider that every company should pocket $3000 or more (depending on the country) per developer per month.

Now about a bit of fact.

Flutter is really cool. It doesn't have a "view" template (everything is practically code) but it has a hot-reload that works really fine and the code is aimed at one task: mobile (now it also allows websites but who will create a web with flutter anyway?). It runs consistently fast. Cons: To learn a new language (however, Dart is quite MORE-OF-THE-SAME)

Xamarin, for another part it has thousand of tools available such as Telerik, Devexpress, Syncfusion so it will speed it up considerably the development process (if you are using Flutter or React, then you are on your own). The performance is also quite acceptable, IMHO, it's on a par with Flutter. The major problem: the tool is unstable and buggy. It is annoying, but it is usable. It has hot-reload but it is inferior to Flutter. (btw, I am more seasoned with Xamarin). Another cons is you can develop for Android, IOS and UWP. UWP is almost dead but it doesn't hurt to have an extra feature.

React Native. Well, it is not really "native", the performance could vary considerably and the "framework" is made by crystal (you change it into something and it breaks in pieces), also some features are a minefield. Not recommended unless you are an expert. It also has Hot-Reload (in the style of Xamarin, i.e. similar to refresh a page). React Native is for those only-trick-pony-developers that only know 1 language (javascript) and wants to program everything using it. It won't work.

IMHO, Flutter wins down, it's hot reload is awesome, the language is (as I said), more of the same, it works fine.