So at what level???

[Spatula]

So at what level or musical education and or professional positions can one consider themselves a concert pianist? 

[timothy42b]

Hah!  This one I can answer confidently.

You are a concert pianist when somebody is willing to pay you to be one. 

This is purely market driven and it is pass/fail.  You are worth it in the opinion of the employer, or you are not. 

(This goes along with my theory that no compliment or criticism can be trusted.  The only thing that counts is if they hire you again.  That is for any gig at any level, not just concert pianist.)