Hello Redelia,
To ship standard post a package needs to be more than 50% bound printed matter. If it is not it needs to be less than 1 pound. Removing the book put it under the threshold and it is well over 1 pound (the maps, pawns, and combat pad do not count as bound printed matter). So it needs to go in 2 packages which increases the shipping cost. It could go in 1 package through priority mail but that is still $3 more expensive. Shipping it in 2 packages through standard post does increase the cost but remains the cheapest shipping option.