According to BrandWeek, Match.com spent $92 million in media in 2006, and $145 million between January and October 2007, per Nielsen Monitor-Plus for broadcast, print and outdoor, and Nielsen Online and AdRelevance for online.
Starting a dating site? You need at least $500k to promote your site enough to drive traffic and media interest to the point where your site is showing up regularly in the news. Exceptional homegrown PR and a novel angle for your site can reduce the number, but not by much.
Makes me wonder at how Markus self-promoted PlentyOfFish. I gave him a lot of grief for being so self-aggrandizing, but his effort certainly did pay off.