A few years ago we had one motor go out for our motorized Roman blinds. I found the manufacturer in Colorado and the manager found only three motors in the whole USA that would fit my application. Just so you know... if you hang new fabric on the old mechanism, then you may have a tough time finding parts, like replacement motors, for the old mechanism in the future.
If the price difference is even close to 50%, then I would strongly consider a new mechanism with the new fabric.