1% or less. Threads work because the content is already on the screen.

I suspect that a decently large proportion of the readers will click who would have scrolled down, if you sufficiently engage them with three or four tweets followed by a link promising they can read the whole thing as a nicely formatted article.

Or heck, just tweet the whole article as a thread, but have a link to the blog version somewhere near the top. "Read in article format here ...".