An interesting middle ground might be writing it in C# (of all modern languages this possibly has the best features / tool-support ratio), but run it on Linux (Mono) and against e.g. PostgreSQL.
Assuming you want to dev on Windows (because of said tool support), you'll still pay licenses for Windows on the dev boxes and for Visual Studio, but not when hosting (or scaling, for that matter).
Assuming you want to dev on Windows (because of said tool support), you'll still pay licenses for Windows on the dev boxes and for Visual Studio, but not when hosting (or scaling, for that matter).