The $100 "Blades & Whips" edition includes all three. The base game priced at $60 (currently on sale for $40) only includes Darksiders 3.
It's actually cheaper to buy DS3 and Fury's Collection: War and Death (DS1 and 2), since both are $40, so $80 total.
You're forgetting to factor in sales, and the fact that the $100 bundle also includes the season pass for D3. If you are willing to pay $40 for D1 and D2 (which you can get on the playstation store for $12) I can't help you there. I don't know what the DLC would cost normally, but, if you want all 3 games, $52 is pretty nice.