If you have it done in the simplest way a ring beaten to shape and a open wire mesh by a silver restorer the cost would be marginal, they would probably have such items in stock needing only minor adjustment. A more elaborate pierced design would cost more and you would need a silversmith who specialises in that type of work.
The nicest option would be to find a silversmith who produces designs you like and get them to design something to suit but in their style. The cost would then be related to their reputation and the elaborateness of their design.
The cost of silver itself would not be high.
It is not sacrilege, more homage :|