This would depend on how you have things setup and whether or not the options_id and options_values_id pair is for a given products_id to make the same price or if "all" options_id and options_values_id pair are the same price regardless of products_id ...
For ALL products_id with ALL options_values_id to be 4.00 you can use:
UPDATE products_attributes SET options_values_price = 4.00, price_prefix = '+' WHERE options_id = 12;
For ALL products_id with the same pair of options_id and options_values_id you can use:
UPDATE products_attributes SET options_values_price = 4.00, price_prefix = '+' WHERE options_id = 12 and options_values_id = 13;
For a given products_id you can adapt the code above to be:
For ALL products_id with ALL options_values_id to be 4.00 you can use:
UPDATE products_attributes SET options_values_price = 4.00, price_prefix = '+' WHERE options_id = 12 and products_id= 27;
For ALL products_id with the same pair of options_id and options_values_id you can use:
UPDATE products_attributes SET options_values_price = 4.00, price_prefix = '+' WHERE (options_id = 12 and options_values_id = 13) and products_id= 27;
NOTE: before attempting any of these, you will want to backup your database ...
NOTE: the commands can be run in the Tools ... Install SQL Patches ... from the Zen Cart Admin