I have noticed in scion catalogs that these rims usually are the ones on the xBs. Are these wheels worth the 1800ish that the dealer tacs on?

Nope, it's all dealer mark up for the stuff they sell in the catalog. Those wheels aren't worth that price, especially since you can get much better rims and tires at the same price.

The only good thing about purchasing parts from the catalog and installing them at the dealer is that it will not void your warranty if anything ever goes wrong.