You're clearly missing the boat by a mile here. The skill of developing software is transferable to different languages. Choosing a language for its skill availability is saying that you're too lazy to hire developers competent enough to learn a new language in a short space of time. If you're hiring people who can/will only write code in $language then there's something wrong with your hiring policy, or there'd be no reason for multiple languages to exist.
Also you're flat out wrong about solving the same problems in different languages. It may be possible to solve all problems in Java or Ruby, but it is not possible to solve them in the same way - or more specifically the best, most economical or most maintainable way.
To bring skill into the equation means no one should ever have written anything in Erlang because few people could write Erlang - but people do, because competent software engineers can learn Erlang.
Also you're flat out wrong about solving the same problems in different languages. It may be possible to solve all problems in Java or Ruby, but it is not possible to solve them in the same way - or more specifically the best, most economical or most maintainable way.
To bring skill into the equation means no one should ever have written anything in Erlang because few people could write Erlang - but people do, because competent software engineers can learn Erlang.