They're based on Phil's approximations of how much he pays. As I recall, he gave the $1500 for the WA condo and said he paid similar for CT. If you have a more accurate estimate, by all means, please provide it so we can get a better idea of what his monthlys are.
One thing--the mortgage payment probably includes money for property tax and homeowners insurance as well. Mine does, at least. So depending on property taxes in WA and CT, that might explain why they're similar.