Would it have been good for ppc marketers if all Google, MSN and Yahoo had equal market share?

[Success With Dany]

Would that bring the cost down or it's better that Google dominates while MSN and Yahoo are 2 and 3?

[Lucid]

If all three major search engines had equal share of the market, that is, people would use each search engine equally and presumably would have relatively the same amount of advertisers, I believe the cost would be about the same on each for the same keywords.

The reason I say this is because it is us, the advertisers, who set the prices. Having three equal choices would not change that. Each of these PPC engines work in basically the same way. Your position is determined by the basic CTR times bid formula. Unfortunately, there are too many advertisers who don't understand this. They are the ones driving prices up because they want better position and keep jacking up their bids to achieve this and driving the prices up for all of us instead
of trying to improve their ads.

The reason there is larger prices differences right now is because there are less advertisers on some engines in some niches than the others. Less bidding wars thus keeping the prices down. If most advertisers used all three to maximize their reach, the prices would be be about equal.