I don't understand why everyone says to be mindful of price as may not be in bridesmaids budget.
Its your wedding and you're the one whose asked that certain person to be bridesmaid, so why should they have to pay for their attire.
I don't expect anyone to pay for my wedding let alone ask my wedding party to pay for their outfits.
If I was a bridesmaid and I was told I had to pay for my dress, etc, I'd turn around and say "I'd be honoured to share in your special day but I can't afford to buy something I'll probably never wear again". If you can't afford their outfits then that's telling you something.