I presume you mean how to "hang" not "frame" a 200 lb. piece of framed art...
First, I would verify that it actually is 200 lbs. It would have to be extremely large or some type of three dimensional heavy art to actually be 200 lbs.
If indeed it is 200 lbs., a number of factors would enter into its hanging methods. If the frame is hardwood, it may be possible to use some traditional hanging methods such as large mirror hangers and heavy wire with two or three passes of the wire. You probably would need to pass the wire through a hanger attached to the bottom middle of the frame in order to make sure the frame doesn't bow over time unless it is extremely sturdy. If this method is used, you must use two hangers located about three to five inches from the sides of the frame as there would be more than 100 lbs. of weight on each hanger due to simple trigonemtry principles. Also, the type of hooks used would need to be anchorable into the wall studs.
I bet the customer is guesstimating the weight of this piece and it is not anywhere near the 200 lbs. they are stating.
Go look at the piece yourself before quoting your hanging charges.
Dave Makielski