This site seems to have very reasonable prices on Mercedes parts:

http://www.oem-mercedes-benz-parts.com/mercedes_benz.htm

here is the info on the site about the timing chain for a 86-91 560SEL-
PART NUMBER SEARCH RESULTS WITH PRICES

Vehicle 1989 Mercedes Benz 560SEL
Part: Timing Chain

Note: 198 link




Product Brand Availability Retail Our Price

A5100-11944 Timing Chain Iwis IN STOCK $107.00 $67.90

Hope this helps somewhat.

__________________
2004 Toyota Sequoia Limited 4wd
1991 Lincoln Town Car Executive
1991 Cadillac Sedan DeVille
1988 Mercedes 300SEL
1972 Chevrolet Caprice Kingswood Estate 9-passenger wagon
1973 Pontiac Grand Ville
(Prior MB's: 1974 240D, 1985 380SE, 1984 190D, 1993 400SEL)