wellm it will all come down to what brand string you plan to use, and what the shop will charge, ever shop has its own fee's, many will install string for free if bought off them, and many make there won strings too, offering it at a lower price to get business
there are several great strings on the market today, and you do kinda get what you pay for
a top shelf string , been a while is about a 100 bucks installed or was in my area
haven't shot a compound in afew yrs so cannot tell you current prices, but thats what I paid to have my last winners choice string installed on a PES bow
would think its still close or even lower as now a days so many company's to compete