instand1 is right... it really depends on the vertical that you are advertising in. Also, what type of conversion are you talking about? Are we talking lead generation or sales conversion? Lead generation is generally easier, and can also have a higher bounce rate... a sales conversion should have a bounce rate lower than 50% as instand1 states... but there are variances here as well. If you are only selling one product, and you send them to the product page with plenty of info there for them to make a decision on whether to buy or not...your bounce rate could be higher than 50%, and you could still be profitable. I have a client in this exact circumstance, and they made (from Paid Search alone) over 1.8 million dollars last year from one product. So basically, it really depends on what your vertical is... what kind of conversion you are targeting... and what type of service or product your are selling.