Guess at ~$300/stay for the big ones and maybe $100-200 for the little ones if you get a good price
. If your turnbuckles are good that helps. Complicate it a bit further with the fact that new metal isn't necessary better than old metal. All things being equal new is better, but you might end up with some garbage metal with cavities in it making it much worse than your "old" gear
A rigger you trust can tell you what stuff you can keep and what you'll need to replace. All the pins should go. We started with the big ones first (forestay, backstay, uppers), leaving some of the lest important stuff (lowers, whiskers, etc) because it's not really too common for a whisker stay to give and demast a boat.