I have used True Box Shot in the past, and I liked the software. I had someone who was on a tight budget who couldn't go for the $55 fee (it does ebook, boxes, membership cards, etc).
In doing some research I cam across myecovermaker.com
This is an interesting business model. You can sign up for a month at $9 a month and make as many images as you want. If you are a graphics person, you can sign up for $90 a year and save even more. If you are on an EXTREME budget, you can sign up for free and pat $4 per download.
In watching the video, this software seems just as powerful as many of the software titles you use on your desktop. So if you have a digital product you are promoting, and you are looking for an affordable book cover, box, membership card, etc you should check out www.myecovermaker.com (Check out the video below – pretty impressive)