Should I buy my bridesmaids jewelry?

I’m getting married in August and I don’t know what I should do about the bridesmaids jewelry. I was going to buy all the jewelry sets so everyone has the same but it’s so expensive and I don’t know if it’s necessary. Is it realistic to ask them to buy their own and just give them a general description of the kind of jewelry or should I buy the same for all of them and not worry about the cost?