Does I need the gold dust worth 25g to cast Arcane lock or is that out due to Arcane focus?

@hv1hj @ChrisPerkinsDnDDoes ine need the gold dust worth 25g to cast Arcane lock or is that out due to Arcane focus? Confuses me. you still need it

— (((Mike Mearls))) (@mikemearls) August 29, 2016