I think the problem with the market is a complicated one. T1 items are abundant on the market because they are easy to produce, easy to gather ore for, and easy to collect via rat drops. T3+ modules require quite a bit of kernal research. Really though, most independent producers are unable to get enough research to start prototyping out these items. Most of the people in game right now with high research have been funded or carried by their corp -- so it's only natural that the modules they produce are going to be for the corp.

It may sound like keeping things within corps is a detriment to the market, and it is. But that's less by player choice and more by the difficulty of kernal research. The only alternative now are individual producers putting in extreme time and effort to gain themselves the research needed to sell on the market. When a single kernal that you need 2000 of costs 250k NIC, that's months and months of work for a single person -- for one single kernal tree.