Hobarts was based on F105, but it is bigger, heavier and longer, although the armament system does not change aside from Hobart is designed to fire SM-6 and SM-3 while F105 is designed to fire SM-2 only.
There are several changes from F105, including a fully functioning ECM AA/AS package. And also automation upgrade so that Hobart only take 2/3 of F105 crew (180 on Hobart, 250 on F105) even tho Hobart is 1000 tons heavier and bigger.
Other different Is that Hobart is redesign from F105, meaning the Australian have to pay license fee to Spanish Government for Hull Design and US for system licenses (AEGIS System) which mean they are more expensive per ship.
Overall cost is more expensive too as
@madokafc point out we have a shit MFU (Manufacture Union) and they sort of suck a lot of money in a lot of small area, also the rest of the money is investment for ASC ship yard to make other ship, such as the SEA 4000 submarine replacement, Future Patrol Boat and SEA5000 Frigate project.
A few years ago, we had a serious discussion on whether or not just buy these from Spain, which they offered to build them for us for 6.5 billions (for 3 destroyer) and the American offered to build us 3 Flight IIA for 7 billions...but we rejected both offer...
Yeah, our wages are notoriously expensive (Well, some of them are) and the Union in Australia have been trying everything they can to squeeze every last dime for manufacturer job in here, that's the reason why we had a big hit on losing Manufacture job overseas (a lot of those moved to Indonesia actually, you may aware)
But yes, our wages is about 60% more than average Spanish ship builder. But the difference is, our builder ain't gonna build shit but sit on their arse with the butt crack showing....