$90 on steam with the expansion packThere's also an extensive free download of community-based scenarios.
If you remember Harpoon, this is a successor. While similar in a lot of ways, the UI is much easier to use and more self-explanatory - it may not look it at first, but once you start using it you figure out its really much less obtuse than Harpoon. The automated functions that your "staff" can do for you are also much better done and avoid a lot of the illogical and annoying "harpoonisms", such as a carrier launching all of its strike-loaded F-18s for CAP leaving you with all the air-to-air loaded ones sitting on deck, or spamming SAMs at sinking surface ships until they actually go under, especially if you set the (very intuitive) Doctrine and ROE settings correctly. Air refueling is an area that's very easy to manage now; if you order a plane to refuel in the air it will intelligently seek out the best tanker - maybe not even the nearest as tankers will automatically reject refueling requests they can't support.
The game has significantly improved AI and much finer resolution in terms of tracking effects - for example, fighter ACM (dogfighting) is actually simulated and modeled and a lot more factors are taken into account in determining the effects of weapons.
The game also avoids the endless database mismatches of Harpoon. The database itself is not editable by the players - you can edit the properties of units within a scenario, but the edits stay specific to that scenario. The database is left alone, and the game automatically sets the database version to the appropriate one for a scenario so database mismatches are Not A Thing. Even better, the database has a very extensive collection of hypothetical platforms in it so you can, for example, experiment with things like "What if we'd selected the YF-23 over the F-22?"
Ground combat is also simulated much more accurately than Harpoon, although the game is not primarily about ground combat, so doing things above the battalion level, maybe brigade if you have a very land-oriented scenario probably isn't advisable. Still, it will model the fighting fairly well and avoids silliness like "I wipe out a tank company with one bomb" like Harpoon would sometimes have.
Overall, I'm very pleased with it. If you want to try out real combat, I highly recommend it. The databases go back to WWII, so its perfectly possible to fight scenarios like "What if Halsey had formed Task Force 34?" I'm planning to do the "final countdown" scenario - 1980's-era USS Nimitz gets sucked back in time alone and must fight off the Japanese attack force before they hit Pearl Harbor.