Lampard has expressed his disappointment at being left on the bench on numerous occasions this season, fuelling speculation that he may leave Stamford Bridge.
However, Villas-Boas insisted: "We see each other every day and speak every day. He is a player not available at any price."
The Portuguese manager also defended his selection choices.
"With the player he is and the history he represents, Frank wants to be involved all the time. But it's the same for everybody else.
"I have 24 players to choose from and my selections depend on how we want to play a particular game.
"Everyone is fighting to start and a player of Frank's level has a shorter distance to travel to be in the team than others."
Villas-Boas went on to praise the impact that Lampard can have on big games.
"He started against Manchester United, Liverpool, Arsenal and Valencia away with tremendous success.
"His talent is not in doubt. He is always on a fantastic run.
"He has been decisive in the last couple of games with the timing of his arrival in the box to solve problems in the team."