Requesting 200 dpi is a bit strange for my world. Printers are commonly in multiples of 300 dpi, such as 300-600-1200 dpi and even a submultiples at 150 dpi.
When a conversion is done to keep constant image size, the image may suffer. Starting with a 200 dpi image, to be printed on a 300 dpi machine, a conversion must take place wherein every other dot is doubled. Image may suffer. If the image were originally at 150 dpi, each dot would be doubled and the image integrity maintained. If the image were originally scanned or digitized at 300 dpi, no such image loss would occur. So the print dpi is important.
That said, if he wants 200 dpi, send him 200 dpi. Don't argue with a man with money in his hands...but do inquire where that number comes from. He may have a magazine which is printed at 200 dpi. Curious minds need to know.