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The short answers to all your questions though, is "it depends". The answers all depend on the people involved. I've been to weddings where everyone in the wedding party paid for all their own stuff. I've been to some where the bridesmaids and groomsmen paid for their own gown or rental, but the bride and groom wanted everyone to have special footware, so they provided that.
In short, there is no 'right' answer, and it'll always depend on the people involved.