ASP.NET is moving at an incredible pace, the new vNext bits are planned to be officially cross-platform and you can support any number of database backends from a .NET codebase.
I also challenge your assertion that better people seem to use other platforms. You can find people marketing themselves as one thing but preferring another in any stack. This is not indicative of anything more than someone needing a job and meeting the requirements of a posting.
Licensing costs can vary. Between BizSpark, DreamSpark and other programs you can get dev tools out of the way quickly. They also provide Windows licensing for the period you're in the program.
The areas where you can get in real trouble as a startup with Microsoft are the add-on product stacks like SQL Server and BizTalk (shudder). I would avoid these in a new product but do not fear building with the .NET platform.