That's not actual size of the chain itself, that is the size of the serialized data structures that get stored by the daemon. This is done somewhat inefficiently. The actual size is roughly half that.

Also, current transactions on the chain are larger than a long-term average would be (with more usage), because of the relatively high portion that are pool payouts, or spending of dusty pool payouts. Once the typical coin is spent around many times rather than being mined and hoarded or spent a few times, the average will converge to something closer to what I estimated above, which is about 8 inputs, 8 outputs, possible somewhat smaller.