It's the obligation of the bride and groom to get their own wedding party to the wedding site and to provide them with accommodations through the process. It's the traditional courtesy of the honor attendants to assume some and even a great deal of the overwhelming planning and duties -- not the expenses -- of the wedding.
It's completely unreasonable to expect people to pay their own way to an OUT OF COUNTRY wedding.
These are the common courtesy limits you intuitively knew were there, K..
If you are not IN the wedding and your best friend EXPECTS you to be there, she needs to find a way to help you make that happen. At the very least, she should offer to pay your travel one way and provide you with a place to stay that allows you to bring your baby if you want.
You should be able to say to your best friend: "I would hate to miss your wedding, but your dream wedding is way to expensive for me. What can I do to make it special for you if I can't be there?" If she doesn't seem to know what to do either, you could offer to throw her a New Mrs. party when she gets back.
I'll bet you are not the only one who doesn't plan to go, K.. I don't know too many people outside of immediate family who would sacrifice that much to make someone else's wedding more important than their own vacation! So maybe someone gently needs to bring that to her attention? I have friends who got married in exotic places with no friends or family and were thrilled to have a reception party for friends when they got back from their honeymoon (in the same exotic location) But your best friend may be heartbroken when many of her expected guests don't come.
Hope all turns out well in the end ~