I'm experimenting with an MMO game accessible via Facebook, though it is not an RPG. The game was designed with both an FB interface and a regular external website interface from day one. Particular focus has been put on social interaction aspects, just as much as good game play, on the theory that people go to Fb primarily to communicate (ie, not only do they want a good game, they want to show off to their friends and meet new ones
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I've been running a targeted Facebook advert based on FB user location, language, and interests. I'm also running the same advert on Google Adwords with (as close to as possible with keywords and site copy) the same user targeting. I'm only a few weeks in, but some stuff that may be of interest:
1. CPC has been very similar between Facebook and Google so far.
2. Facebook advert has been dramatically more successful. I think this may be partly because my Google keywords and SEO is not yet up to scratch, and the site has not been live long enough for Google's taste. Facebook is also a smaller pond with a captive audience.
3. Getting going with Facebook advertising has been much easier and faster than with Google Adwords. This is because it is so simple to create and target FB adverts, and there is no lead time or SEO needed like there is with Google.
4. Both adverts lag far behind user referrals anyway. Facebook's viral spreading through user feeds is better than advertising. Give your games a FB interface and some way for users to post trophies/awards/activity to their FB profile feeds, and their friends will see it and start coming.
So.. yeah.. no concrete conclusion on CPC - not enough data yet. But Facebook integration will certainly attract users. IMO it is worth doing even if you never try Facebook advertising.
