100-500 USD or so
200-400 USD
Ruger uses a model number, such as 0804, but the suggested retail price of a new Super Blackhawk stainless 44 Mag is $829.
Depending on EXACTLY what you have, it could range from a hundred or so to multiple thousands.
100-1000 depending on specifics
$600 USD
Ruger's web site has a sn date function
100-350 USD
Depends on finish, barrel, condition- ranges from ABOUT $225 for a well used specimen to about $475 for a new-in-box.
100-500
100-1000 USD depending on specifics
Manufacturer's suggested retail is $667. A quick look on Gun Broker shows them at "buy it now" prices of around $550 - $600.
There's no way to answer this question without knowing exactly what needs to be fixed.