This is intended. The first 1% is just to bind it to you.

It's designed to stop people reselling crafted items after they have used them. The items aren't meant to continue spiritbinding beyond 1% until you start fighting higher level monsters in Bahamuts Coil (and soon Crystal Tower).

If SE were to allow people to Spirit Bond item level 70 stuff on any level monster then the materia market would go to hell!