Everyone should question the status quo. Everyone should think about their program and work on it new each year. Have people talk about how they decide what to give. Be specific and candid. Personal testimony is powerful.
People can overhear a conversation at vestry.
Get people in same circumstances to talk to each other. It is a pastoral issue and every priest should know. It is a window on the depth of our spiritual lives. It is a way to challenge people. The loudest objectors are usually the smallest givers.