The first link you found is for SQL Server 2008 R2, which is a very old version. And the text was inaccurate already at the time it was published, presumably a holdover from even older versions of SQL Server.
Legend has it that these "costs" that the optimizer works with relates to metrics on a some developer's desktop in the late nineties. By time, these values has lost all contact with the real world, and today they are just abstract metrics with no real-word meaning. The later URL points this out.
It is also true that the original default is considered way too low with modern computers. The default remains 5, since Microsoft are not keen on changing the defaults for backwards-compatibility reasons. But the recommendation in general is to set this parameter to 30 or 50.
What would be the right value for your site, is something that only can be determined by experimenting.