what are "e-covers" exactly? Are these those "boxes" that you only create digitally to make the impression that your software product, which is only sold online, could very well also be "real" software which could be sold in a real-life store? If so, you can probably create them quite easily. All you need to do is to create the graphics for each side and then let something put them on a box template. Well, I'd use Photoshop and Illustrator for it, I guess, myself. But I guess that's not really a _cheap_ solution.
Or do you mean something with templates etc.?