They are far from "almost identical". EOS is built to handle smart contracts, while Steem is more of a traditional PoS blockchain. You can create apps on EOS that would not be possible with Steem.

As for the reason why it's valued so high, my 2 cents on the matter is that it is because a lot of people believe that it will be a better version of Ethereum, and eventually replacing it as the number 1 smart contract blockchain.