The fans own the pitch at Stamford bridge. They need to agree to any move otherwise Chelsea can't redevelope there. Last few times they've tried they refusedI’d be shocked if they could build a new stadium at Earls Court for 1.2 bn.
Although if that’s the net spend ; assuming they flog off the old ground for development etc ; but even so I’d be surprised given they don’t actually own the land at Earls Court ( and just as much as their real estate is worth a lot ; so is land in West Kensington and environs ) .
To sum up ; others will know better than me but 1.2 bn seems implausible to me .