The Santa Rosa pattern by Syracuse China (Syracuse, New York) in the Federal shape date to the years between 1949 and 1966. A set of 120 pieces in this pattern has a retail value of $450 to $500 dollars (wholesale $150 to $200). The prices you see on Ebay are asking prices by normally high priced dealers and not what the item is likely going to sell for, so one can't really use that as the only gauge of value.
If you give this set to a local auctioneer on consignment or to an antique dealer, you will get $200 for the set. The $450 to $500 price is if you sold each piece individually online or sold the set to an individual through Ebay/Craigslist/ or similar venue.