My 3x3x6 tent cost $100. I cannot build a sufficient tent for that much money. By sufficient I mean structurally stable to hold a light, opens and closes easy, light-tight, sturdy, fall apart when I touch it. Those sorts of things. But someone else is going to post the tent they made for a nickel from stuff gathered around the house.
Something to consider. Autos do not need to be grown in a tent like fem/photo because they do not need dark periods.