Most likely 1945 dollars, as they didn’t crank up production lines again. Also, they made hundreds of thousands if not millions of them in WW2. Economies of scale and all.
But even so, a Mk84’s (2000lb dumb bomb) per unit cost was $3100 back in 2000, not exactly a lot worse compared to literally any guided missile. Even adding a Paveway guidance package to the dumb bomb only adds ~$25K to it.
Back in 2000 they still had a metric butt load of 500/1000/2000 pound bombs from the Vietnam era.
That said, the only way missiles are cheaper than arty for putting warhead on forehead is to get a contractor to come up with a new precision/stealth/hypersonic/cyber-ready/environmentally-friendly/insert-latest-buzzword-here ‘wonder-weapon’.