how to change Default value for cost in Financial Summary.
Not quite understand your request. Do you mean you don't want "x $1,000" to be displayed in the cost details section title? If yes, you can set the parameter BUDGET_IN_WHOLE_DOLLARS to true in the server.conf parameter.
Doing this will make the value in financial summary displayed as it is, for example 150,000 will be displayed as 150,000 instead of 150.