Adjusted Pinny lines are -19 -110/+19 -105, adjustments of more than 1.5 points not possible, but at 19.5 it would probably be -105/-110 or so.
You cannot compare buying points at other sites with Pinnacle. At other sites you usually pay an additional 10 points per half point, or 20 if it is a key number, while at Pinny it differs but is generally a lot less.
Why Pinny chooses to keep 17.5 at that strange juice I could only take guesses at, and I don't like to do that.