They do hope to offset some of the cost with their Pledge Manager, though.
From the post:
When we designed the expansions we really wanted to include 3 new double-sided Map Tiles in each one. We had a really great push at the end of the campaign, but came up just short of the totals needed to add these to the project.
This has weighed heavily on us since the campaign completed, because we really want Journey to be the best it can be. We found a great way to reduce the cost of the art and now we have 3 Map Tiles that we are really pleased with. Perhaps it will surprise you, but the shipping cost is the biggest remaining problem. But guess what, we will add them anyway! Yes, the Spider Demon Expansion now includes 3 Map Tiles! How could we resist giving these to our backers?
You know the pledge manager opens soon. The honest truth is that we need to get to $460K in pledges to cover these extra map tiles. Regardless of the final total, we are adding the maps, but remember dollars raised now helps get the finances back to where they need to be.