Prices for Steem vary widely across the net right now, because the exchanges (with the possible exception of gopax) haven't yet got their Steem wallets working again after the hard fork.

Our site analyzes those prices to determine what price to use, so we've had to make choices about which price we trust most during this disruptive period. We are using a price that seems to be the "consensus" price across the exchanges right now and it's on the low side of the total range.

Coinmarketcap is estimating considerably higher because it is mostly using Huobi's price (because they report the highest volume).

Long story short: if you agree with coinmarketcap's price, you should buy from us because we're selling it lower than coinmarketcap's price (and we can actually deliver the Steem, which few if any exchanges can do right now), so it's a great deal by that view.

On the other hand, if you want to sell your Steem, you might want to wait until you can transfer it to Huobi instead of selling it to us now, but I wouldn't place any bets on the prices being the same by the time they re-enable their deposits.