If you can find a metal fabricating shop that has a shear, you will be in business. You won't lose any of the swarf and as long as the ingots fit into the shear, it will cut them smaller. I did exactly that when I worked in a metal fab shop years ago. Cut the pieces into about 2" long chunks.
You might get some funny responses on the phone, but you might also luck out. Just make sure you explain to the person on the other end how big your ingots are, so that he knows if they'll fit into his shear.
Some places might also call them Ironworkers, but you just need to explain what you want done.
As for cost, it might be anywhere from mild to wild, or free, depends on the mood of the guy on the other end.