It can't even replace my internet bill because of the cost of multiple people on the plan! Where is the new competitor going to come from in a market this is so difficult to break into due to price and monopoly concerns? Without that competitor, where are the drops in prices coming from?
If you had five equally popular search engines, they wouldn't really compete prices down anyway. The number of searches (supply) would still be the same & advertisers (demand) would still be the same.
The only reason MSN & Yahoo (not to mention real obscure engines) still earn less per click is a sort of market imperfection: It's complicated & time consuming learning another system & running parallel campaigns. For an extra 5-10%, it isn't worth it for small campaigns.
Monopoly or not, they are not manipulating the market. It manipulates itself.