How much can I reasonably ask for my 3 year old, only sporadically ridden BMC URS 1?

I sadly never got deep enough into cycling to justify having a 3000€ bike standing around in my garage gathering dust most of the time.

SRAM Apex group, carbon frame, DT Swiss rims. Almost no signs of use, never had an accident with it.

How much should I ask? I'm in Germany if that matters. Thanks!