For just a few more days, Dietrich Bonhoeffer Works (DBW) (16 volumes) are $100 in Olive Tree Bible software. I have not seen DBW in Olive Tree, but have reviewed the app here. Their iOS and desktop apps are free, so if you like Bonhoeffer and have the cash, this is probably the best price for his complete works in English that one will ever find.
(Except for checking the books out from your local theological library, which is even cheaper!)
UPDATE: It would appear this sale has ended, a couple days before the date Olive Tree had given me via FB. Despite the miscommunication, the folks at Olive Tree have let me know the set may go on sale again in the future. To your library!