$800K per round seems a bit off - that would be half the current price of a Tomahawk cruise missile. This https://en.wikipedia.org/wiki/M982_Excalibur would be a good comparison and it costs about $80K.

I remember when i first learned about these guns it looked to me like somebody decided to go for a money saving trade-off - land attack with weaker round at shorted distance at supposedly cheaper price per round than a cruise missile. Looking at that one, i can't help to remember another trade-off - to save money F-35 engines aren't made stealth ...