Well, the Shuttle engines were, on the order of $50M or something like that. But the Merlin-1D, according to a former SpaceX employee on Reddit, is in the ballpark of $1M per unit. They've really streamlined the design for mass production, so even if thrown away after a single use, the Merlins are actually much cheaper than the Shuttle engines even if you take RS-25 reuse into consideration (9 launches per one RS-25 unit in average - so about $5-6M per engine-launch in just amortized manufacturing costs?). They're also much simpler and sturdier, much like the F-1 engines - despite not being designed for it, it turned out that those could have been used for about twenty-thirty times without major problems and without major component replacements. The RS-25s pretty much required general overhaul after every flight.