Ok, sorry for using the term "not fair", I should have probably said that it's "unsound" to judge the speeds of current dynamic languages on mono/.net to the speeds of v8, SpiderMonkey, etc. The cause being that the speeds of the latter were fueled by very high browser competition and a lot of resource investment. Dynamic languages on .NET got the benefit of neither of these, so it should not be surprising that they are slower than their native implementations (which also get better funding/bigger communities). It would have made more sense if Microsoft or other companies threw millions of dollars at the Iron* languages and still couldn't make them fast.