Java Mission Control is free for development (see: Oracle Binary Code License Agreement for the Java SE Platform Products and JavaFX ("B. SOFTWARE INTERNAL USE FOR DEVELOPMENT LICENSE GRANT").
For development you can use the:
-XX:+UnlockCommercialFeatures -XX:+FlightRecorder flag to unlock the Flight Recorder.
If you would like to use Java Mission Control in production, you will have to buy the Java SE Advanced (Desktop / Advanced / Suite) license: http://www.oracle.com/us/corporate/pricing/technology-price-list-070617.pdf
NEW MUC Airport Workshop: Migrating Java Client (Swing / Java FX) to Web Standards