i think it's still fine, the cost not too much as well. might not as big as big N where people expect the genres there.
it's natural, 1.5M is not low, it's still in the good number. people who thought it will hit 10M is kind of expecting city car vs super car, unless You are Takumi (initial-D), it might never catch up with other big games.
the good thing is, if it considered good income, it would continue, and soon there will be other games in the genre, spawned by Sony. this will broaden the approach variety and good for smaller project for the studio under Sony.