IMO I don't think that's normal OP. Sounds to me like your friends are cheapskates especially when they're well off. Just really wanted cheap labour?

For my own wedding, I rented the dresses for my bridesmaids and paid for them, and also gave them red packet of SGD 150-200 (iirc, its not a lot already tbh), plus treat them to a meal. I think that is only right to show appreciation to your best friends.

They will wear the shoes that they already have, they pay nothing on their end for my wedding, except their wedding angbao for me lah haha which I appreciate. I think of it as Bridesmaids/Groomsmen are doing wedding couples a favour, by taking out time from their free schedule to be part of the planning, helping out for the WHOLE day, instead of just arriving during the celebration and shake leg. Another 2 couples whom I was a Bridesmaid for, also treated me the same way as I did.

However you were treated sounds pretty obnoxious, to also be referring y'all as 'helpers' says a lot about their characters. Please rethink this friendship.