Dear Linda:

KBB or Edmunds prices do not apply well for old Mercedes diesels, especially W123 (e.g. 240D, 300D) , W126 (e.g 300SD), etc... These cars are always in great demand. You may get them near or even lower than KBB prices if you are willing to take a risk in bidding and buying them on Ebay. Otherwise, expect a minimum of $500-1000 above KBB prices if it's a in-person private sale.

Eric