[fermigier]

Invader has explained his business model here: http://www.space-invaders.com/about/

"Is it possible to own a Space Invader? How do people acquire one of your works? -> [...] Finally, for people who wants a unique art piece, they can seek for an Alias, which is the exact replica of the unique work in the street. There is one and only Alias for any past or present works present in the streets. Every Alias comes with a signed certificate of authenticity. Art Collectors should contact Over The Influence for any available pieces."