Need 60 Image Cutouts - Background Removed

For this project I will email you 60 hi-res/medium-res images of machines gears as well as a few pieces of machining equipment. All images have a background (some simpler than others). I need the background removed and the resulting image returned to me in PNG format with the background color transparent. I need these images to look FLAWLESS - I should be able to add a solid background of any color or image and the item in the foreground should look seamless against the background. Cheapest bid will win...I will only pay once the resulting images have been reviewed & accepted. Needing to get this completed by 1/31/2010