If you happen to be fortunate enough to have a Christian or Jewish seminary school located in your community, you may have a way of acquiring useful bible study tools at a fraction of their usual cost.  Very simply, these schools are often you need of selling extra copies of materials on their shelves — perhaps they are older copies that are worn out and are being replaced by a newer edition, or perhaps they have duplicates that they don't need to keep around.  Many of these seminaries will have scheduled fundraising events throughout the year where they bring these books off of the shelf and out of storage — and you can buy them, often times for just a few dollars each.