Alex -- Yes, community is key for social grids, but it is a separate issue from price, and I don't think the two are related. OSGrid has a community, and some fo the lowest prices around. InWorldz has a great community, with tons of mentors, and a premium price compared to OSGrid (but a huge bargain compared to SL, of course). Other commercial grids have high prices but no communities to speak of.
I guess good profit margins can help with community in that they can give the grid owners some money with which to run promotions, hire community managers, etc.... but in this case, low basic costs would enable them to charge the same prices as everyone else but have better margins which they could put towards community building.
Meanwhile, many groups have their own communities all set and are just looking for some combination of low prices and good service. For example, companies already have their employees. Schools already have their students and teachers. A role playing guild already has its members.
Some of these mini-communities may be perfectly self-sufficient on a small grid. Others might prefer to turn on hypergrid so they can interact with other communities, or go shopping, or attend training events or music nights or whatever -- thus allowing them to have their cake, and eat it, too.