If his rate was $100, it's really now $200. If $200, now $400. (For comparison with another remote worker who works at full speed.)
the actual rate (high or low) wasn't really the point. It wasn't a statement of whether it's expensive or cheap, just an observation that someone who works at $30 "twice as slow" (i.e. half expected speed) is equal - in terms of $/feature - to someone works at $60 at full speed on a like basis - even if that basis is also remote.
(Also, even though $/feature is the same between the two, it's worth bearing in mind that the cheaper guy still takes twice as many days.)