YSM costs vs. Google Adwords

I only can tell from my experience and from what i hear from people i know (which may not be the general statement for all niche) that Y! cost 1/3 of G. however, most niche convert low due to worthless clicks from their partner sites. some niche convert better than adwords though. you just have to be lucky with a niche or have knowledge which niche that converts and how to convert them

Does anyone make me more clear.......

thanks in advance