Realtor got locked out ... who pays ?

[Marci Stein]

House is for sale - gave clear instructions to not lock bottom ( no key ) . Put black tape over knob . Showing agent ( not listing agent) was last one there but denies locking it. 

Cost $50 to open — I don’t think it’s fair to have me pay it , but no one feels it’s fair to pay . 

Man who opened  door is friend of listing agent’s husband . My idea to ask him to open it , but never thought they’d ask me to pay him . 

WWYD ???