I'm guessing that not too many people have taken Scholar to 20 on my server (Najena), so Grim Spellbinder App3 is- to me anyway- outrageously priced at between 1g75s and 2g. Though I need even this version of the spell very badly, I don't have that much money and, if I did, there's no way I should have to sink everything I have into a single spell or equipment upgrade. I can't imagine what the Adept version of that spell goes for.
On a related note, is it just me or do I see all too few Summoner Adepts being offered for sale? That leads me to believe that, like cloth armor, Summoner Adepts drop at a much slower rate than do spells/skills/equipment of other classes. For instance, I've never seen a Dust Blast Adept offered for sale at any price, but I've seen tons of various healing Adepts. I know that it's not too many Summoners around- not that many people who are real gluttons for punishment like myself.