Bridesmaids buy their dresses unless you have the budget to fit the cost for all of them. Its costly for sure and to go over budget of your day. Part of the gift to give them on the day of the wedding can be earrings or jewelry to match their dresses. Our MOHs bought their sarees and paid for their blouse tailoring.
My friend just had her wedding this past weekend, she paid for the dresses but had them pay for their hair and makeup. I'm getting my girls to pay for their dresses and I'm paying their hair but they are on their own for makeup. It's really up to you and your budget.
In my experience, typically the bridal party pay for their clothes. It's pretty much an unspoken clause that there is a cost involved when one signs up to be a bridal party member (bridesmaids or groomsmen). How much that cost is will depend on the couple.
I would personally be flexible and work with their budgets. Though brides often want to control every detail of their wedding, having close friends and family feel forced to spend beyond their means to satisfy a particular aesthetic feels like the antithesis of bringing loved ones together to celebrate a joyous occasion. That's just me and my two cents.
Honestly it depends. So I am paying for earrings for the day of, their hair and make-up and their nails. They will be purchasing their own dresses, shoes (if they want to get a new pair) and any other accessories they may want to wear.
I wrote my wedding party a document of anything that I expect from them and what they should expect from me so there was no awkward moment when a time comes on who will be footing the bill.
They can pay for everything or you can pay for everything, or the best case; mix and match on who pays for what.