Generally $150-300, and usually from 100-150 images. These are experienced pros with good portfolios. Some photographers also sell individual digital images for ~$25 each. $50-60 would be a bargain, but might be appropriate for the clients in your situation. Consider that an 8x10" print from mpix costs $2, factor in what you'd charge for prints and how many prints you typically sell to a client, and set your price for digital images accordingly.