The only way you are going to get 10x, with roughly equivalent people is if someone is using a wholly inappropriate language (Ruby vs Forth for web apps, say), or if you can avoid writing libraries because someone has already written them.
This is one of the positive network externalities involved in programming language economics: the more people involved, the more likely it is someone has already written the code you need. Of course, these effects are not so strong that everyone gravitates to only a few languages, but they are certainly a consideration.
By writing your own language, unless it makes it very easy to take advantage of some other language (the JVM languages are a good example), you are pretty much guaranteeing that you will have to do this work yourself.