I took some amazing timed exposure digital pictures in Carlsbad Caverns, and want to print at least one to poster size. I've been looking online, and one of the best deals I found was Costco, who will print 20x30 posters for $8. I don't need breathtaking quality, and the camera is only 6 megapixels, but I would like it to be accurate to the image I took.. I will probably build an inexpensive frame for the poster, myself. Is this the best deal, or is Costco's poster printing to be avoided?