Although your estimate of the effectiveness of a treatment is the primary factor in making decisions, there are many other things that factor into deciding on a treatment. Two examples are the cost of the therapy, and the side effects.
These factors will modify your "cut-off value" for each individual therapy. For example, you presumably would require less evidence to accept something that is cheap, easy to take, non-toxic, and doesn't interfere with effective conventional therapy than you would to accept something which is expensive, with severe side effects, and which requires you give-up a conventional therapy which is proven to be highly effective.
Click on specific cut-off modifiers for a discussion of each.