I just can't determine the advantage of a custom bike at this point (having no experience), so seems foolish to spend the money on a bike I can't even test and hope it will be 250% better! Maybe after this initial tour or sometime down the line, I will.
The advantages of a custom bike are the following:
1. You demand a unique bike built just for you. No one else has your bike. Its unique to you only. It has whatever you want on it. Whatever color.
2. You require a unique, different, non standard size frame. Smaller or bigger are the usual changes. But some people have extra long bodies and short legs, so they need a bike to fit them. Custom. Standard factory frames are built for the average person ranging from about 5'4" to 6'4" tall with normal sized legs, torsos, necks, heads, feet. Their bodies fit within the bell curve of normal. Bike manufacturers make bikes to fit them by the millions. The normal sized person does not need a custom bike for fit.
I don't need a custom sized frame. Many manufacturers make perfectly sized bikes to fit me at the factory. And some manufacturers don't make bikes that fit me very well at all. Colnago being one of them. Short top tubes. But I might want a custom to get different handling from normal, extra stiff, or extra plush, or more tire clearance, or unique braze-ons, or...