EVE and Darkfall are two examples of games whose economies work fine with no level restrictions.
You shouldn't need level restrictions in a sandbox MMO to make meaningful economies, it's usually used to make your character feel more unique in games with much larger communities, like WoW and SWG.

How is there this confusion between players that one thinks you can max everything and one doesnt? Is it really practical to max everything? Is the game really enjoyable when limited to only X number of skills?