Comparably priced is just a starting point...you have to get there in order to have any hope of penetrating the market.

But the beauty of most of these alternatives is that they are renewable...once economy-of-scale drives the prices down they will stay there. There will be no underlying non-renewable commodity cost to spiral out of control (ie oil).

Most folks are looking at biomass based feed stock...totally renewable. If the demand goes up, you just grow more. The only possible cost variable might be some energy required to refine the stuff, but hopefully grid power will become less reliant on fossil fuels also.