Bitbucket somehow manages to maintain a service of similar or greater quality or reliability and has free unlimited private repos. Github is charging more because they can, not because it costs that much to maintain.
People who think that Bitbucket is on par with GitHub are the same kind of people who said that StackOverflow could be cloned in a week. You focus on features but fail to see all the painstaking attention to detail that went into creating these sites.
IF you use the web-interface consistently. If you don't use the web interface much, or use it for simple text diffs, bitbucket is perfectly viable.
One funny thing about github is they put so much effort in to being able to diff images and other files, yet their space limits are too low for private repos, if you are versioning anything other than just text files.