~$300-$375 for 30lb. tank on ebay completed items. Don't know if the link will "hold" for long.

http://motors.search-completed.ebay.com/R-12-30_eBay-Motors_W0QQcatrefZC6QQcoactionZcompareQQcoentrypageZsearchQQcopagenumZ1QQfromZR10QQsacategoryZ6000QQ samotorscategorymapZ6000QQsas_partneridZ2QQsbrftogZ1QQsofocusZsoQQsoitemstatusZ2QQsotrZ2

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)