I'm going to force other bridesmaids to buy more expensive dresses.
Why do you want to force them to by the more expensive dress?
Because they were the only ones who wanted to stay at my hen party after the bride left.
It is nice to want others to be part of your wedding but it is not good to ask them to spend a lot of money. It could put them in a hard spot and cause them hardship.
I invested a lot at the wedding, so they should do the same.
I suppose you could ask them to, but don't be surprised if people back out in response. People don't like spending too munch money.