Any sale of a search engine to Google is an asset/talent sale, right? They're not going to operate a competing search engine brand (aside from that one they do user testing at) -- they're going to assimilate its technological and biological distinctiveness into their own.
Google has 23 billion a year in revenue, substantially all of it from two products. Operating an internal competitor to Product #1 will not move the needle. Its, quite literally, less likely to make them less money than changing the shade of blue they use.
Google offered them $30-40M before they launched in '05. They should have taken that.
Back then Munjal (the CEO) was writing an interesting blog about starting Riya - worth reading the old posts: http://munjal.typepad.com/